There are pluses and minuses. My non-scientific impressions (take these
with a grain of salt, my experience with these has not been deep) ...

	ncr-based cards	
		* SRM can boot them (as long as the chip isn't newer
			than your SRM)
		* the driver has been a royal pain, but does seem to
		  always get beat into shape

	adaptec
		* common, which is good; SRM usually cannot boot them.
		  Expensive.

	buslogic
		* not the highest performance driver, but I've been very
		  happy with my buslogic card, and I think they are cheaper.
		  SRM can never boot them.

	isp
		* hi end, but rare, you may get to "discover" new problems
		* I'm told srm can boot them :-)

As far as where to buy:
	
		* visit www.resellerratings.com

For SE scsi, buying new kind of makes sense, see the above URL. For
differential, the stuff is extra-expensive new, but extra-cheap used,
as people don't generally appreciate the value. I got my buslogic 
differential card new, since buslogic is usually quite cheap, but
I got my differential ncr cards used, and got used or new-but-surplus
diff drives. For some reason, there are lots of WD Quantum Atlas II's
around...

To find something like a "used ncr differential pci scsi" adapter on
the net is a real challenge, but I did accomplish it once...

Hope this helps...

	ross.harvey@computer.org