Is it just the body shape and scale length that makes the Jag appeal? If it's sound, neither of these is gonna hit the mark... at all.
If it's just the scale length and body shape... I dunno it's a tough call. Both instruments have their down sides, while having similar basic features (humbuckers, hardtail, single 3-way switch).
The Squire is cheaper, which is nice, and the colour options are better... the bridge is kinda weaksauce. The pickups, I really don't have anything to say there, though SGJarrod says they're decent. You'll have to be a bit careful with the basswood body, as it will dent and mark up super easily.
The Blacktop, ASAIK is fairly sturdily built, with a better bridge/tail, but, it's suggested that you might want to swap out the pickups... maybe you wouldn't.
I'm sure this has been no help at all, as I have no idea which way I'd go... I'd probably go for a Blacktop Jazzmaster
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