As a user of a few CAD systems I would recommend UG. A close second might be Cadkey, except that I wouldn't trust the new owners.
The advantage that UG has over most systems is that you
1)can have multiple parts in one file
2) you can work any way you want, want to create just wireframe,fine! Just want to work in surfaces,fine! Want to work in sloids,fine! Want to have wirefarme,solids,surfaces in the same file,fine!
3) parts can be started using a simple wireframe, or a sketch if preffered. You can start a solid using a 2D wireframe, or a surface, and then you can add details to that solid later using skecth based geometry
4)drafting package is excellent, I prefer drafting in Cadkey, but UG is a close second.
5)UG has ahuge range of options that can be added, FEA,NC etc
6) UG is ridiculously expensive, however with some arm twisting UG dealers have been known to drop the price of UG seats dramatically
7) UG has an annoying habit of supplying different builds. The system I use is the P1 design package, I can do drawings, but I can't export 2D drawings. Other peoples packages can.
I would get a dealer to come by and demo the different CAD packages. However make sure that when they demo the product that you make the dealer or demo'ing person deviate from the canned demonstartion. This will show how flexible the package is, also it will tell you how well the dealer knows the package
It doesn't really matter what package you use, once your upto speed and are familiar with the chosen package, they're all pretty good!
Good luck Dave