Definitely go for Prowl. The fact that he's a star higher than the other two bots alone, makes him the best option. But even if the other bots were at the same star as Prowl... Prowl would still be the best option. And... What @KakaMax said is very good advice.
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I thought you were talking about 5 star ones which would lead me to support cyclonus more, but at lower levels...
If you don't have 5* bots, just Pretend only 4* bots exist.
The rest are just forge fodder and not worth your time anymore.
Your 3 star bots cap at a rating of around 1500... About the same as a rank 2 4* bot!
A fully maxed out, full forge and full sig 4* will be ranked about 4800.
Prowl has lots of abilities and useful stuff. You should awaken him, and he does quite a bit of damage.