I own both an ETX and a LX200 GPS (that was my answer to my own situation -- I needed two different things and the perfect scope has not been made yet).

Which one to get depends on two things:
-- Money, and
-- Intended use.

ETX 125 is perfectly fine for many uses.
ETX has the following advantages over LX200 (besides the lower price):
-- sharper image, and
-- portability,

An 8" LX200 can show you more distant objects, and more detail on closer objects.
(But you may not care about that enough to pay much more.)
One area where an 8" LX200 GPS would be recommended over an EXT 125 is imaging.
If you need to take a lot of quality pictures or do CCD imaging frequently, LX200 has the requisite features (larger aperture, fine focuser and mirror lock).

If you are planning to do mostly visual observations (with an occasional photo/CCD use where results do not have to be perfect) than it's just the matter of money and personal preferences.

Portability is (too) frequently overlooked -- many scopes end up gathering dust because they are not easy to set up.
(I've had one large scope exhanged for a smaller one because moving it and setting it up was too much trouble.)

Remember: a small scope in the hand shows much more sky than a large scope in the closet.

Good luck.

M.M.