First, know that specific product recommendations are off-top here. But I'll point out a few points to consider as far as features.
Number of keys
Do you plan to learn piano/keys? 25 should be fine for playing most melodies or bass lines separately, but it will tough to play both at the same time as you would when learning piano. So if you only want something to record individual parts into a DAW, 25 will probably be fine. But for performing as a keyboard player would, you'd probably want 49 or more.
The key action is a matter of how hard it is to push the key down before you trigger a note. A real piano key has a bit weight to it and requires more force to push it down than a synth. This is a good thing for dynamics because it makes it easier to play the softer notes which in turn means that it's easier to play a wider dynamic range of volumes.
MIDI controllers that attempt to mimic that piano feel will be marketed as "hammer action", "fully weighted", or something similar. Those with no weight at all might call it "synth action" or avoid mentioning it altogether. In the middle is "semi-weighted".
Again this comes down to if you want to play like a piano player. If you are playing anything non-synth (piano, electric piano, etc) then being able to play dynamically is pretty important and I'd look for something with hammer or at the very least semi-weighted action. Other than that, it's up to taste. Try some out at a music store if you can to see what key feel you like.
Do you plan to play percussive sounds like drum patterns? If so pads are pretty useful. You could always use the keyboard keys as triggers. But the keyboard keys have a longer "key travel"—the time/distance between when your finger hits the key and when the note is triggered—and pads are generally more responsive and conducive to percussion parts. That said pads have a range of feels as well and just because a keyboard has pads doesn't mean they will feel good. And you can always add another, separate controller that has pads.
Knobs and Sliders
These are certainly nice if you plan to use them. Setting them up as DAW control is one thing (ex. channel faders). But if you play a lot of synth sounds it becomes really useful. Part of playing synth is manipulating the params like filter cutoff or whatever else and being able do hear those changes while you're playing is really useful. You can certainly do it in the software with a mouse after the fact but it can be hard to do it while you play without the tactile control of a knob/fader. And just as with pads, you can always add them later via another controller.
What kind of room do you have on your desk? Do you favor something more compact? Do you mind the extra price for more keys or hammer action or whatever given feature? Are you ok with something suboptimal for now with a possible upgrade down the road or would you rather spend the money to get the best one right now? There are no objective right or wrong answers and buying the right product for you usually depends on reconciling these kinds of tradeoffs.