Some good advice above.
As a compressor junkie for the last twenty years, I've learnt one thing - every bassist wants something different from a compressor. A lot of folks love the Trace Elliot dual-band comp. I couldn't shift mine fast enough. Just didn't do what I wanted. Some worship their valve comps, while others say they're too noisey. Only you know what you want it to do to your sound. My last comp was a modded Boss CS3 - fantastic amounts of squish and a low noise floor.
Thing to remember about nearly all [b]PEDAL[/b] compressors is that the vast majority of them are based on one or the other of two designs. Range of controls, tone suck and noise levels will vary between these pedals, but they are still based on one of these designs. There are exceptions (among others the JoeMeek above, which I'm dying to try. But again it's based on the JM rack comps which have their own sound)
As Simon says, your best bet is to go for a properly spec'd rack unit. Play with it for a while and you'll know your settings for punch, squish and limiting and all points in between.
What am I using now? Nothing at the moment. I've decided I don't like compressors after all