I am happy with my recently purchased beta57 after a few gigs.
I tried the SM57 and after buying what turned out to be a counterfeit (to save about $20) the first time round, I bought the real thing from a Shure dealer. The fake mic would not drive a long cable to the desk (it had a far higher resistance measured at the output - around 300ohm cf 20ohm for the real deal). The real SM57 fixed the long cable problem, but it never worked well on my bass live - it was way too boomy in the 'rubber band' mounted position.
After an opportunity to test out a beta58 I finally bought the Beta57 for its form factor. It has the clarity / defined tone I needed on my bass. The proximity effect on the Beta bumps up around 200Hz, where the SM is affected lower down.
The other advantage of the beta is the tighter supercardioid pattern. Shure dealer prices on new Betas in Australia have dropped significantly in recent times - mine cost the same as my fake SM57 did a couple of years ago.
You might find that cheaper imitators of the Shure mics are not as immune to handling noise. Both the SM and Beta 57 seemed really good in this respect.
You will almost certainly be ahead buying the real thing if you take resale value into account. I gave my fake SM57 away to a local small venue (with appropriate warning) because it was too late to complain on ebay or track down the seller - 100% depreciation
I hope these observations help