Garmin uses a non-standard protocol; Bu353 uses the standard NMEA protocol. Normally this would be a problem, but thanks to Franson GPS Gate you may use an "ordinary" GPS unit and make it work even with Garmin nRoute.
More info:
http://franson.com/gpsgate/guide.asp...platform=winxp
Don't buy a Garmin receiver just because of this one "issue". It's really a non-issue w/GPS Gate. And GPS Gate has other very useful features.