More specifically:
Pharos iGPS-500 vs GlobalSat ND-100

People's opinions, though a review wouldn't hurt. I don't think phoronix has ever reviewed GPS products.

This is what I have
. 2 grams lighter (how much is a gram?)
. newer NMEA version (3.1 vs 3.0)
. better linux reviews
. "looks" (picture) solid. American made I think.

. supports two more NMEA sentences (lat. & long. + velocity vector). However, these can already be deduced (via computer) from other sentences.
. 2 dBm more sensitive
. 28 more channels (doesn't matter though, only ~10 NAVSTAR satellites in the sky at a given time, so)
. power requirements are slightly less (more in the range of usb)
. supports EGNOS (European) as well as WAAS (American)
. weird baud rate despite data refresh rate similar to competitors. (gpsd compatible though)
. First revision firmware has a date issue. Fixed in the second revision.
. "looks" like a usb stick. Everyone knows how fragile those things are inside
. unknown. zilch. nada. no reviews. Taiwanese company, though (I think).

The gpsd compatibility page reports similar interoptability for both devices. The iGPS-500 isn't marked as having gpsd automatically started by udev, but that could be simply an oversight. I also couldn't find any information comparing the SirfStar3 e/lp with the M-Star MSB2122. I guess I'm simply looking for first-hand reviews before buying.