I love webers and love SUs... I have both and have run both... the webers are good but as JD said, be prepared to learn how to tune and refine them as most tuners will only get you in the ball park- they will get max power sorted on a chassis dyno but low down drivability will not likely get a look in...
SUs are cheaper but to be honest they still add up, but the tuning price should be cheaper than the webers.
Be prepared for about $1200 for 1 3/4 SUs with good linkages and rebuild on a decent manifold. Then about $800 for dickin around and tuning on a dyno. Or a few hundred if your prepared to self tune.
As for a street car, I tend to agree, the SUs give better street performance from my comparisons, although the webers are also quite good if you run conservative chokes. There is not a heap of difference, just that the webers have a fixed choke setup which means you need to comprimise with either the bottom end or top end... you pick a power band and choose the chokes accordingly- ie 3000-7000rpm. The SUs are more forgiving due to their variable venturi design.
From my back to back comparisons (bum dyno only as yet) the webers excel at higher rpm. My SUs pull off the line much better than the webers. I can see why the webers are the pick for circuit cars as they spend all their time between 4000-7000rpm and this is where the webers will excel.
The SUs should give a better 60 foot time in a street type drag car (launching at say 3000rpm), hence why I imagine the drag racers seem to run the SUs.
Furthermore, the drag guys would also lean towards the SUs as its a right pain in the jatz crackers running webers on methanol as you need huge main jets and it causes tuning gremlins... SUs can be adapted for meth a fair bit easier.
If you are keen on webers, dont bother with the FAJS- no resale value and only marginally cheaper... I would run a FAJS carb if they were half price but theyre not, so stick with the genuine as you will regret buying the FAJS imho.
You could buy some 1 3/4 SUs in good nick and throw them on, at the end of the day if you dont like them you can sell them and the whole exercise will not cost you much.