Depends on your skill with synths but also in processing the results you get from synths. Making a kick for example is not particularly hard, it's just a pitch envelope on an oscillator slamming up and down 64 semitones real fast. What's hard though is making it sound truly BIG, I've not managed it versus some of the processed samples I've got, probably because some of the best samples have been through studios with may more expensive gear than I have at my disposal
Most people imo use samples for drums, or goto products like superior drummer/BFD or plain use breaks and just chop em up. Also imo I just love the sounds of a live drummer, it's why I think it works well to sometimes layer a break along with your own drums.
I usually use samples, but find synthesised kicks can sometimes be good for layering underneath, especially if you want to add some more weight to the sound. You can also match the pitch of your kicks and snares with the key of your tune, so that's quite handy...
You cannot beat the sound of a real kit. Period. But, adding a little pitch bending sine wave underneath for beefiness or a tad of FM noise to imitate the sound of the beater itself meeting the drumhead can make a dull sample shine all the more.
If you happen to come across a snare in a pack that so happens to immediately gel with your mix, use it and move on.
Typically, this is a rare occurrence as snares in sample packs usually come in two flavors: Flavor 1: Snares that have been left ample headroom for layering; Flavor 2: Snares that have been processed heavily that require a bit more effort if you want to layer.
I find great success in layering the mid/hi end with a real snare so I can get the "sizzle" caused by the chains vibrating against the drum. For low end, creating a synthetic drum can be great because you can tune it properly in relation to the key of your tune simply by hitting the right note as opposed to having to pitch shift. Adding a bit of overdrive can also add some beef to the harmonic content of the sound creating a greater perceived loudness which is always a plus.
Me and my mate used to be in metal band and he had an empty beer keg and we used that in one of our tunes, complete slipknot rip off and the tune was shocking haha and in answer to your question I use samples, never even thought of synthesising them, haven't mastered the art of it yet, bet it would be a real useful tool to have nothing can beat a lovely old chopped up break doe.