speed has a very chemical feel to it, if you know what i mean. it just seems dirty to use. that said, it just tightens and puts a lot of stress on your body. it lasts a while though, so you'll be feelin good for a decent amount of time. coke is just a feeling of godlyness, but it is over very very quickly. it feels natural, and it's good to party with.
I prefer speed (amphetamine/methamphetmine) because it is much cheaper, much longer lasting, and much more potent for how much it costs/how available it is.
Both are good in their own right. If you're going with an amphetamine (your "speed"), go with adderall or dexedrine pills. Street meth that isnt straight crystal is usually pretty cut and I would recommend against it. Coke is nice but is way more addicting than speed IMO. Way more expensive too. Amphetamine gives you a really energetic, euphoric (higher doses 50mg+) feeling and you do pretty much everything better. Coke is more of a feel good drug, but it's gone way faster than amphetamine and it can be hard to find good quality. The coke high lasts for ~15-20 minutes, an amphetamine high lasts hours. Unless you have a good bit of cash to spend, I would go with amphetamine. It's not a very "dirty" or "chemical" feeling like Philosopher4420 said.