I won't get involved in "which is better for the bike", except to say
that I use a fork mount for my fenderless road bike, and a "whole bike"
mount for my fender-equipped touring bike. The "whole bike" mount is
bulkier and cost more, although I did get it on sale. In all honesty, I
don't see a significant difference in total effort required to get the
bike onto either rack and secured, but I've spent enough time tinkering
with my bikes that popping a front wheel off is no big deal.

Just to add to the confusion, there is a third option. There are a
variety of carriers that attach to a receiver hitch installed on your
car, that appear to me to be much more secure than the trunk-mounted
strap-on rack you are currently using. Advantages I perceive are that
fuel economy and vehicle aerodynamics are not as adversely affected, you
don't have to worry about low garage entrances (but do be careful
backing up), and the risk of damaging your car's body work is much less
than with roof top or trunk mounted racks. Trunk access is easier than
with the trunk-mounted racks, but how much so will vary from car to car.
Some of these racks pivot out of the way to make trunk access easier.

Simplest of all, of course, is to pull the wheels off the bike and put
it in the trunk, or fold the rear seats flat and put the whole bike in
the trunk.

mark
Bob Weissman wrote:
I've been using a trunk-mounted strap-on bike rack on my car, but
it doesn't exactly inspire confidence that my beloved bike won't
fall off at freeway speeds.

I'm starting to look at roof-mounted racks and see there are basically
two kinds: the kind that hold onto the fork and require you to
remove the front wheel, and the kind that allow you to leave the
front wheel on.

Which is better? Obviously the fork mounts require more work, so
they must have some other advantage? Is there a problem with the
whole-bike mount which would cause me to regret choosing it?

(The bike is a 2007 Trek Pilot 5.0 and the car is a 2000 BMW 528i
sedan, if that makes any difference.)

Thanks,
- Bob