Old thread I have already wieghed in on, but I guess the question continues. I currently own a USA 55-94D with Bart PUPs and preamp and a Skyline 55AJ with Lakland single coil PUPS and MK1 preamp. I also have owned a Skyline 5501, a DPLE II Skyline Glaub with Darkstar and B&B neck, a Skyline JO5 with Fralins and a Skyline Glaub with the stock (at the time) Fralin PUP.
The 55-94 is in every way superb: 8.5 pounds, perfect balance, absolutely even response all the way up and across the neck. Killer with flats for funk or Motown sound, crystal clear with rounds for a more modern touch. The Lakland 55 neck is my favorite after almost 50 years of playing. The differences between USA and Skyline have been, for me:
Skyline
Averages 1.5 pounds heavier, sometimes up to almost 3 pounds depending on model.
Gloss finish back of the neck as opposed to satin
Brushed metal bridge saddles as opposed to chrome
Brushed metal tuning gears (but not the paddle itself)
Plastic nut as opposed to bone
There may be other differences I am not aware of.
Of the Skylines I have owned, only the JO5 exhibited the old Fender "dead spot" around the 5th fret on the G string. Since I have never played the USA versions of the Skylines I have owned, or the Skyline version of the 55-94, I can't testify to differences in sound, how necks feel or fit and finish. All I can say is that I have been happy with every Lakland I've owned, and the only reason I don't still own all I have purchased is that I am one of those guys who buys basses all the time and sometimes has to sell them because I simply don't use them as much as I thought I would. And maybe I'm addicted to buying.
Right now, the 55AJ fills a place in my arsenal that was missing: Active bass with single coil PUPs. It is a snarling beast with rounds but also capable of clarity and, at least preliminarily, I think the B string sounds even better than the B on the 55-94 did when I used rounds on it.
If you can afford the price tag for a USA, by all means, get one -- you will not regret it. If you just can't do it, spending $1,200-$1,500 on a Skyline is far from a bad idea. I have a Steinberger L2 that cost $1,500 used and a Rick 4001C64 that ran me $2,200, and neither feels or sounds as good for all applications as any of the Laklands I have owned. If I had to have only one bass, it would be the 55-94, hands down.