As it turns out, I have owned a Gretsch Jr. Jet, a Squier Mustang, and a Squier Jaguar SS in the last 2-3 years. Loved the sound of the Gretsch but it had 3 issues I didn't care for. The body is plywood and HEAVY. The finish chipped easily. There's no contouring whatsoever so it really aggravated my forearm. Also, this particular bass had a very irregular neck with severe differences in fret height. Kind of a worst-case Chinese product. I traded it rather than fix the neck.
The Squier Mustang was fine but IMO it didn't play any better or have the tonal diversity of the Squier Jag SS, and the Jag was over $100 cheaper. The neck is a bit faster on the Jag as well, but if you like a thick baseball bat neck then it won't be for you. Also, the string-through aspect of the Mustang was off-putting to me. I mean, it's hard enough to find decent short scale strings. Finding medium scale strings (which the Mustang requires) that suited me was even harder. The neck pickup on the Jag is a true P-pup as opposed to the Mustang pup which I thought was brighter with a bit less low end.
This may be useful or meaningless to you, but I'd recommend starting with the Jag. If you don't like the Jag then I'm not sure you would like the Mustang any better. Of course, YMMV.
