When creating electronic beats, I have a hard time deciding if I should really use a synthesizer to sequence my whole rhythm section. Sometimes I end up using samples or recording something close to what I want, so I can process it until I get there.
Whatever the chosen method is, I'm never sure of it.
What are the advantages and disadvantages of each? When should I use one over another?
There is no blanket answer to your question. It depends. "It depends" isn't very useful though, so let's try to dive a little more into it.
Generally speaking:
Sample: Less complexity, less flexibility.
Synthesis: More complexity, more flexibility.
But it's not that simple, and the weight of those cons and pros depend on each specific scenario. Do you want realistic cymbals? It can be very complex to do that through synthesis, and the result is often not "real enough", but through sampling you can do it very easily (you can end up liking the less-realistic synthesized cymbals more though, who knows). Do you want a sawtooth with even harmonics panned opposite to the odd harmonics? (like here) How do you even achieve that through sampling? You go the synthesis route.
Many synthesis techniques involve sampling, so that generality becomes harder to hold. I'm assuming with sampling you are referring to simple samplers.
It depends on the limits of the technique, preference, and your skill set.
Are you experimenting? If so, it's a good idea to use both (and others) and hear what you like the most, maybe using both at the same time. When I'm designing kicks sometimes I like to mix layers of drum-kick samples and fast-frequency-swipe type bass drums (like in the Roland's 808).
Do you already have something in mind? First ask yourself if what you have in mind is achievable with both methods. If so, ask yourself which method will have the best impact in the sound. This is not exclusive to sample vs synth, but also useful when deciding among synthesis types (FM, AM, granular, additive, whatever). If you are not sure of which one is better suited for the job, try both and hear which you like the most.
The answer to your question will vary depending on the sound, on each individual case. Only experience (or a less general question) can answer it consistently and accurately. Once you study and understand the different synthesis techniques (sampling, subtractive, additive, FM, AM, pulse modulation, phase modulation, phase distortion, wave guide, granular, wavetable, etc) you'll be able to decide which method better suits the sound. There is no absolute "better" or "worse" here.
When should I use one over another?
The big advantage of using samples is that it's easier to make your hits sound like real instruments. If you sample a snare drum, and use that sample, it will sound more like the real thing vs. a synthesized snare hit, which will more likely sound synthesized.
One disadvantage of samples is they may need to be cleared (you may need permission or may need to pay to use them) for commercial work. Another disadvantage can be that they are more work to create if you are making them from scratch. Personally I find programming a synth easier but sampling from scratch more gratifying.
The big advantage of using synthetic sources is that they are more likely to fit in the genre of electronic beats. If they want to be big and nasty, starting with certain synths can get you most of the way there quickly.
My rule of thumb is if I want 'real' sounding hits, I'll use samples of real instruments. If I want not so 'real' hits, I'll use synthesized sounds. BUT sometimes I'll use samples of synthesized hits. I don't have a lot of classic drum machines, but I have quality samples of classic drum machine hits...
My rule gets further blurred because I also use samples in my synth, processing those samples with filters and mods to make them sound more synthetic. :-)
It's really a choice as to what you want to use for your sound generators. It's also a preference that develops with regards to your work flow. Some days I despise my sampler. Others I just have to have that John Bonham kick drum.
Whatever the chosen method is, I'm never sure of it.
There is no right or wrong answer. You as producer need to decide what sounds good to you. If you are doing it for yourself, then your taste will ultimately dicate that choice. If you're doing it for another reason - maybe you're brought on to produce for another artist, then you need to temper your taste with the needs of the song/track/ultimate destination...
