Reasons why mapping is better than modelling:
-Mapping is usually done by all by yourself(as opposed to one person modelling, one person UVing, one person skinning, one person animating, etc)
-A good map can last forevr, a good model can get old and be replaced
-Mapping communities aren't filled with realism whores who strive on correctly mirrored guns.
-Mappers tend to work much longer on a project than a modeller, thus bearing a generally better result
-Modellers only build worldly things. Mappers build the world itself.
-The majority of models are weapon hacks. 99.9% of maps are all from scratch.
-Mapping comunities don't have stupid nicknames for their members such as Darkeh(Darkstorn, a very well known modeller for his ak47 model)
-You can spend more time runing around testing an MP map by yourself than running around testing a custom model.
-There are no real specialities in mapping, unlike modelling which has animators, skinners, etc.
-There are no noob map requests like there are model requests.
Reasons why modelling is better than mapping:
-Modellers are far more recognized than mappers.
-There are far more modelling communities than mapping ones.
-If you build a model you are almost certain that someone will download and use it.
-Models can be used anywhere for anyone. Maps have to be used by everyone at once.
-Modelling has virtually no limits(provided that you have a good enough computr to keep up. Just keep adding bodies and 512x512 textures and you can do anything).
-You can usually request a model and get it, you cannot request a map.
-You can play with a custom model for longer than a custom map without getting tired of it(in most cases).
Just thought I'd put these out there, if anyone feels like adding anything go ahead and post it.