Dedicated GPS unit? Or use PocketPC?

When would it make sense to use a dedicated GPS unit
rather than software on a laptop or PPC?

Yes.. or No.

It *entirely* depends on your personal circumstances and how you intend to
use it, if there was one best solution everyone would be using it.

Sadly since you make no mention of this no advice can be given.

Sorry

I can "see" myself using this unit mainly for walking
and hiking purposes. So compactness and long battery
life would be needed.

Okay cool. You basically have two options, all in one, or pocket PC using
bluetooth.
Personally I've found the all in one units to be rather heavy, which might
mean that it's not the best thing for walking and hiking.

Then you've got Pocket PC, these are quite light and small enough to keep in
your pocket. The bluetooth GPS receiver can be placed (say) on the top of
your rucksack to get a good view of the sky. The advantage with PocketPC is
that you are not tied to any particular software package. For example you
could use memory map to get proper topographical maps for your walking. But
also have TomTom Navigator which will give you turn by turn directions in
your car. You will not likely get that kind of flexibility from a dedicated
unit.

Battery life might be an issue. From experience you will likely be able to
run the PocketPC for around 4 hours, 5 at a push maybe. Not a problem in the
car, but could be if you are on long walks. The solution of course is to not
keep it powered up the whole time, if you only have the unit powered up for
say 10 minutes out of every hour it should last for ages, the rest of the
time it will quite happily sit in standby using minimal power.

Of course this assumes you want the unit to have maps etc.. you can get much
cheaper handheld solutions which just give you your current position and
heading which you can then plot onto a paper map (I would always advise
taking a paper map as a backup anyway, GPS should only be a useful extra)

I see

What abt getting a minimal unit that has some maps in
it but still small and compact and super ling life....
and then using that in "tandem" with a PPC if I need
more capability?

IOW....could I use the "small" dedicated GPS unit as an
"antenna" to a more sophisticated unit (PPC) if needed?

I'm thinking along the lines of a Geko or eTrex with
some maps built in. But hooking it up to say a laptop
or PPc if needing more features.