It could make it better, or it could not make a difference at all. In Holland, T-Mobile's 2G network (which is what you'll be on when you'd switch off 3G on your iPhone here) is considered more reliable, less spotty (i.e. more coverage) and less crowded than the 3G network, so call drops would be less frequent on T-Mobile's 2G network than on the 3G counterpart.
To answer your question, in general, 2G coverage is larger than 3G coverage, so as a rule of thump, reception of a 2G network would be better than a 3G network. Reduction of call drops totally depends on your carrier and location.
Message edited by rachidfinge on 11-08-2009 at 09:05:15 PM
It works the same way with CDMA roaming too, if they see a 'prefered' tower then they will try and maintain that connection, even if it's spotty, and thus your overall reception is worse. Essentially it's going to depend on the strength and penetrating power of the frequency used for 3G for that tower/area, as to whether it would be consistently worse or just occasionally. It's hard to tell without testing it yourself, but it does have logic behind switching.
