A scanner _is_ a densitometer.  I don't know of any commercial software
for the easy use of a scanner for absolute measurements.

Occasionally there is discussion of this issue, try Google.

TTBOMK the best B&W film for scanning is color negative: either the
B&W versions or plain 'ole color film turned to B&W in Photoshop.

Paul,
You pose a very good question here. I really can't give you any definitive
answer, but here are my thoughts anyway. Mike has a good point in that
color film allows you much more control over the image in PS than BW. If
however you prefer to control your negs in camera using color filters and
grads, then stick with the BW. It certainly has more dynamic range than
color when processed correctly. The question needs to be asked however, do
you need all that dynamic range? In my opinion - no. The big advantage to
BW negs is that you can optimize your image for each scene with different
development. Ansel Adams took great pains to expose and develop his negs to
print on his paper of choice at the time. The main reason for that is
because BW papers are quite limited in their dynamic range. If your
negative wasn't exposed and developed to produce a good print on a #2 grade
paper you're going to be fighting all the way to get a good print. To a
lesser extent the same holds true for scanning your film.  Most modern film
scanners do have a greater dynmaic range than conventional BW papers, so I
would say, as a start at least, that your going to have to develop for more
contrast than you had been. What you need to watch for is making sure you
expose and develop mostly for the shadows because if the detail's not there
your out of luck. There are so many variables between the scan and the
final print, that optimizing your development is going to be a daunting
task. Different scenes will require different negative development as it
did with conventional printing. You want to get a scan that will be as
close as possible to producing your desired print without any - or minimal -
PS adjustments. Sure PS has lots of ways to control the image, but
remember, almost all of them throw information away as a result. Shooting
digitally in camera raw is a much less lossy process however. Personally
for me, those days of plotting curves for different developments are a
thing of the past. I much prefer shooting digitally in camera raw where I
can digitally develop the image with minimal loss in quality. I hope this
helps a bit.

B&W or color?  For B&W scan a Kodak density step wedge to verify your
scanner's sensitivity and linearity.  Then photograph the MacBeth chart with
an 18% gray card, or better yet a really good step wedge positive.  Use
bracketed exposures and "standard" development.  If you don't like the
result, but the step wedge scans are acceptable then vary development until
you get acceptable results.  See how your B&W images render the various
colors into neutral density.

For color, shoot the MacBeth chart on color negative and transparency film
with bracketed exposures.  Check the scans on the color patches and the step
wedge along the bottom.  You may be surprised to find that some of the color
patches don't scan much like the chart, especially so for the transparency
films.  Look for good yellows.  These are hard to reproduce with color
films.  Note that your scanner is linear (CCD/CMOS detectors) and that the
firmware applies considerable signal conditioning.  Color printing is
inherently non-linear and is designed to reverse the non-linearity that is
present in the film recording.  Once you get the best scanned result that
you can, you can expect to need additional color correction through
non-linear gammas applied with PhotoShop or PaintShop Pro before your
digital result matches the original chart.

In my limited experience (I have only been working with digital scans since
about 1987), B&W is most difficult to render to digital format because the
scans are inherently contrasty.  B&W scanning is like printing with a
condensor enlarger onto grade 3 paper, so you might want to explore
fine-grain (read that as smooth-grain) developers.  Almost for certain the
D76 1:1 that prints so well won't give you the same kind of result when
scanned.

A final remark is that I agree with your procedure.  For me, color printing
is always a PITA because I can't control parameters with anything like the
precision that can be had in the digital world.  Also, film stores about
72Mb in a 35 mm frame.  That's possible with digital cameras too, but at
high cost and greater inconvenience.  Unfortunately, it's not easy to invert
the process and turn your high resolution digitally processed scans back
into color negatives that can be printed conventionally.  Being locked into
ink jet printers and expensive paper and ink isn't all that attractive to me
for the finished product.  Especially so if you want large print sizes.