How does it compare to the SS Jag? Is it a noticeable step up in feel or in tone?
I've got two SS Jag's. One stock and one modified. Honestly, they're very similar.
The new Mustang has a deeper, fuller tone, the tone control is more effective,
its got clear coat on the headstock, different color options, different body shape,
different control type and layout, and of course - the Fender logo.
But to your question - if you want the Mustang P/J, but can only afford the Jaguar, don't sweat it.
You won't be missing a
whole lot, and nothing that can't be taken care of in the future.
The finish, fit and overall outward quality is near as good on the lower price unit.
I can't speak to the electronics, other than the sound, as I don't know much about them.
With the Jag, you get two volume controls and a tone control. With the P/J Mustang,
you get a 3 way switch with a volume and tone control.
So, how you work with it is different.
Playing them back to back, the Mustang sounds better to me at all settings,
but sound is subjective and someone else might hear it differently.
I've recorded them both at home with similar settings - P/both/J, with tone full on and full off,
and while the P pup is pretty close when used alone,
anytime the J is brought in on the Jag, it sounds a bit nasally in comparison.
Also, you can't do something with the Mustang like have the P full on,
and the J at 80%, like you can do with the Jag, for example.
With the switch setup, it's all or nothing.
Thinking about it that way before trying it, I wasn't sure if I'd like it.
But it sounds very good in all positions and settings.
One other thing to consider is the body shape. Besides the obvious different look,
the Jag has a body contour, and the Mustang is slab cut.
That makes a difference for some people, but I'm fine with both.
Hope that helps you out.