home garage compressor: how many CFMs?

[Konstantin Bogach]

Sorry for bringing it up again.  I remember seeing thread with similar
topic some time ago but  I searched archives and  could not find the
answer to my dilema.
I need to buy a compressor and I am looking at two craftsman units:
a) 6HP,  oil lub, horisontal style, single stage, 150 PSI max,  6.8/8.6
cfm at 40/90 psi, 25 gallons
b) 3.5HP, oil free, upright, dual stage, 175 psi max, 5.1/5.8 cfm at
40/90 psi, 25 gallons

I like everything in b) except that I am concerned that I think that 5.1
psi in on a margin where most tools work.  Is it right?
Plus, I am not sure how they rate their compressors - conservatively (I
doubt) or optimistically (most likely, I am afraid).  So, it could be
4.8, maybe.  b) works veru quiet, upright style attracts me too.  I am
not going to run sanders. Both a) and b) have same price.

I would appreciate if you share your experiece of how much CFMs you need
to run most common tools and help me to make right choice.

Thanks a lot in advance.
Konstantin.
200tq '89  (about to start R134A conversion)
200tqa '89  (same as above)
UrS4 '93