The type of razor you're using has an impact of how good the shaving cream will work for you. If its an electric I've found out the hard way that the jelly type creams can clog up the blades and basically ruin the razor pretty quickly.
One of those Mach 5 razors really don't need a ton of lather of any sort, (claims my dad) but also they get clogged with the gel's pretty easily too, so usually when I use that its just the cheap crap from a can, and I never use a lot of it.
I love my straight razor though, and probably out of getting a little excited every time I use it, I always put a ton of cream on my face. Its pretty much pointless to lather up a ton if you've only got a few wiskers but... *shrugs*, I enjoy my private time

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Usually when I'm using or buying the stuff in the can I make sure it has some type of oil in it, like Vitamin E or some Aloe Vera mixed in, it just feels nicer and smoother to me.
If you're a big hairy mountain man then I'd pay the extra cash and get a brush with some fairly decent soap, because razor burn just isn't worth not paying.
I've never noticed a really HUGE difference in creams or soaps. Some dry my face out really badly, others burn for some godforsaken reason, and some just screw up the razor you're using. But I will vouch for creams that come in tubs that you lather yourself and use a brush with. I'm not sure if its the different soap or what, but I think it works the best.
There's always just a little personal preference thrown in there too, so you just pretty much find something you like and hope it works good.
Note: I have no ACTUAL beard, but I do have to shave my upper lip every day less I look like someone dumped finely ground pepper all over my lip. Also, very bushy side burns.