Step Down or Track Glide slope on GPS overlay approach

I have just recently acquired a Garmin 430/WAAS for my Mooney 201. In
practicing approaches to familiarize myself with the unit, I went up
with an instructor to get some advice/tips. I had flown a GPS overlay
approach (NDB/GPS Runway 5 KLWM, Lawrence MA) previously in VFR
conditions and tracked the vertical guidance provided by the GPS and
loved it ... very stable approach and no need to dive/level/dive etc.

Then I went up with the instructor and did what I thought was a great
approach (also NDP/GPS 5 KLWM) and he was upset I didn't fly it more
like the "original" non-precision approach by identifying fixes with
cross radials and doing the stepdowns.

So that is the question. Which technique should be used and why? If I
give up the "track the GPS glideslope" approach I feel I'm giving up
the advantage of a very stable/controlled approach configuration and
not sure what I'm gaining in return.

Comments from the experts??

Final questions: With the WAAS GPS on this approach, can I descend to
the lower minimum based on identifying the final stepdown fix if I am
just flying the GPS's vertical guidance? Where are the answers to
these questions provided?