EXS 24 Logic Sampler Users Group

I've posted this question on a few other forums that I'm usually on,
and I haven't been able to get an answer...

I've got a semi-technical question regarding the CPU load generated
from playing a sampled piano vs. other sampled instruments.

As anyone who's ever played a software piano knows, if you play too
many sustained notes for too long with too low of a buffer setting
you're going to run out of CPU headroom and get crackles & pops.

Through my experience playing multiple instruments through my laptop
I've noticed that my piano sample libraries will deplete my CPU
headroom TREMENDOUSLY faster than my Scarbee electric pianos - even
though the pianos are running flat & dry and the EPs are running
through AMP models, reverb, tremelo, & EQ and other effects.

Both the pianos and EPs are being played using the EXSP24 out of Logic
Express 7.1.

My thinking is that since I'm playing the Scarbee libraries with all
the keys sampled at 12-14 different velocities the computer just has
to stream the audio samples, but with the pianos using 3-4 velocities
of every 3rd note there is alot more pitch shifting and filtering
going on. Is my thinking correct, is the filtering & pitch shifting
that the EXS is doing causing that much headroom bite over the Scarbee
libraries? Is there something else going on?

This leads me to my other question... If my assumption is correct,
does this mean that I'll have more CPU headroom if I go to a larger
piano sample library? My system has more RAM space to spare than CPU
headroom, and I'd greatly aborb a longer load and more RAM usage in
exchange for more CPU headroom and a lower buffer setting. Is this the
reality of the situation or is my logic flawed?

Here are my system specifics:
Apple Powerbook G4 17" (1.5GHZ / 1.5GB RAM)
Logic Express 7.1
Buffer Size - 128 for Scarbee, 256 for Pianos

Here are the core sample libraries I use live:
Scarbee RSP73 (12V Lite)
Scarbee WEP (14V Lite)
Garageband Grand Piano
Logic Yamaha Grand Piano
SampleTekk Rain Piano