I am very new to guitar and chords.
I wanted to learn to play and sing the song "What a wonderful world".
However, while looking for the chords, I found 2 different versions of the set of chords:
https://tabs.ultimate-guitar.com/tab/louis-armstrong/what-a-wonderful-world-chords-7427
https://www.guitaretab.com/l/louis-armstrong/227008.html
Which one should I use? Ideally, I would like to understand why there are two different versions.
There can be different chord renditions for the same song for several reasons:
1) They correspond to different recorded versions of the song. The song structure (e.g. number and sequence of verses, chorus, repetitions, etc.) may vary.
2) They can be in different tonalities, either because of 1) or to allow singing by different voice ranges, or, sometimes, to make it easier to play on different instruments (e.g. guitar and piano).
3) Chord finding by ear is not an exact science, particularly with songs that have complex harmonies and/or many simultaneous instruments and vocals. Different transcribers arriving at slightly different chord types in specific parts of a song is not uncommon. It doesn't necessarily means one of them has made a mistake, sometimes it's impossible to tell for sure.
4) Simpler versions of the song, with simpler chord shapes, may be created. Sometimes this noticeably changes the way the harmony sounds, but it allows beginners to play the song.
In the examples you give the ultimate-guitar version sounds to me quite good and faithful to the Louis Armstrong recording I have.
The guitaretab version is indeed a simplified version, and to me it doesn't sound too good. It's in the same tonality (the chord shapes are given in the tonality of C, but your are advised to use the capo in the 5th fret, which puts you a perfect 4th above, i.e. F), but the chords don't sound as good to me, some times they sound blatantly wrong.
Anyway, generically speaking, you will always find different sources for the most popular songs, you should try them, compare with the original and try to make your own judgement as to what version you like the most and better suits your playing.
The Guitaretab one is a simplified version of the song so it does not use the more 'difficult' chords (e.g. Fmaj7 in the other version). The Guitaretab version uses a capo on the 5th fret, so for the first verse you're not playing "C G Am Em" but actually "F C Dm Am" but with the forms of "C G Am Em". So you're kind of playing the same chords. Other differences are that instead of the Am from Ultimate Guitar, it uses a C which is the relative major chord of that minor chord (try Googling 'relative minor or major chords' for more info) . It sounds similar but is not actually the same. I haven't tried to play it but I would imagine that both versions sound all right.
The other answers by mbauwens and joseem address the specific song you asked about and joseem did an excellent job explaining the different reasons we often see different "translations" of a given song by different folks.
But I want to address the edited (by Matthew Read) title to provide useful information for folks who come across the title in a search and ultimately want to know how to choose from multiple translations for any given song (other than the one cited in your question).
We know that many songs will be interpreted, transcribed or translated using different ideas on which chords to use where.
Piano based songs (written and performed with piano as the dominant instrument) are the most difficult to translate to guitar because the chord voicings that come easy on piano are often very difficult to translate to a playable chord on guitar.
Here is what I do if I want to learn a new song that is not one I can just listen to the record and hear the obvious chords.
If my search turns up multiple different interpretations, I try a few on my guitar and eliminate those that just don't sound good at all. I am trying to narrow down the possibilities to the various interpretations/translations that sound somewhat authentic - at least in certain places. For example I might like the way one idea sounds good on the verses but might feel another translators version of the chorus chords sound better.
In many cases, none of them will be perfect - so I compare them side by side and come up with my own personal interpretation or translation of the chord progression and write it out on my own lead sheet.
Let me step back a moment and talk about transposing to different keys. In the beginning when I am trying to find the best version, I like to take the key out of the equation entirely because once I arrive at the best interpretation of the chord progression, I can always transpose or use a capo to get to the key I want to use!
In other words I want to know if the best sounding version of the verse chord progression is (for example) I Major - iii minor - IV Major or if it sounds better using a V Major instead of a iii minor (that type info). Once I know which chord types and scale degrees sound best, I can transpose my chord sheet to whatever key I can more easily play or sing in.
After choosing several versions that have elements that sound kind of right, I will save those in a folder on my computer. Then I go to a lyric site and copy and paste the lyrics of the song into a word document and format it so that I have room to write the chords above the lyrics.
Then I will take the song section by section starting with the verses, then the chorus and then the bridge. I know that one of my selected versions may work better on the chorus while another may work better on the verses.
When trying to determine which version sounds best - I play each section while listening to a recording of the song (perhaps using a capo to make the key the same as the recording). Usually every interpretation will start off with the same chord (often a I Major) and may all agree to a point.
As I try out each version, I am writing the chords I think work best on my lyric sheet above the word that falls on the chord change. When I get to the point where two versions disagree, I want to try each version side by side on my guitar - to see which one sounds best. When I decide, I write that chord on my lyric sheet.
As I go through this process, I usually discover after trying each different chord idea in the different places, that some parts of some versions sound great while other parts of a different version sound better. So I take what works best from each version and write it on my new version.
Once I have determined through trial and error what chords sound best to me based on how I plan to sing the song, and have those chords written above the lyrics I pasted on my word document, I try those chord types in different keys with different chord sets and capo positions to find the chord set and capo position that makes the song easiest to sing and play for me.
For more about using a capo to make it easier to play certain songs on guitar or for transposing songs to a different key using a capo (including a handy capo/key conversion chart) click here
I type out my final version and save it as a word document and print out the lead sheet for my notebook. It's a process that takes more time than just choosing the "best" version out of many (that may all be less than perfect), but analyzing the chord progression in this way helps me learn the song on a much deeper level (and helps me as a songwriter as well).
Have fun as you expand your repertoire on guitar!
