Juniper, no argument. Pro's will prefer the SRX as it's a JUNOS box, but the ScreenOS based SSG series will suit small business better.
I wouldn't touch many other firewalls, ASA is still a really exasperating product just as the PIX was, it's not a terribly powerful product, it uses different concepts to most firewalls and it's not particularly intuitive. Sonicwall/Watchguard I still regard as toy firewalls, they might be OK for small business but find me a enterprise which uses them. An honourable mention for Fortigate who make some interesting boxes but the GUI and command line both disagree with me. Checkpoint still have real pedigree and are powerful boxes but I can't think of a reason you'd use them in a new install out of preference.
And those are pretty much the only serious players that come to mind...
Depending on your bandwidth and other needs, I'd say a SSG20/SSG140 would do you fine (SSG20 is small but I've seen bigger organisations than 75 users use them very successfully as edge firewalls, SSG140 should definitely do).