It really depends on what you want to achieve. The SP1 and F1 are essentially different tools for different jobs. Sure, one can do most of what the other can do and vice versa but, they can’t both do all the same things equally well.
The F1 was designed to offer full control over a remix deck, with the implementation of .stem control being, more or less, an afterthought. Not to say that the F1 doesn’t offer the ability to do other things quite well but, its inception was based on creating and playing 64-cell remix sets. For many people, it makes for a really great dedicated effects controller, pairing well with pretty much any other controller setup and/or DVS. And although I haven’t tried it yet, the F1 seems to work quite well for .stem control also. Personally, I would not recommend the F1 for something like finger drumming (or that type of rhythmic performance - whether it’s drum samples, synth sounds, chopped up vocals, or hotcues). The pads feel more like clicky on/off buttons than performance pads (the feel you have on Maschine, MPC, Trigger Finger, etc).
The SP1, on the other hand, has great feeling pads; I actually prefer them over Maschine’s. The SP1 was essentially designed as an auxiliary controller for DVS in Serato. It’s basically Serato’s Kontrol X1; It covers typical deck functions like, browse/load, effects, loops, hotcues, etc. It’s an excellent controller in Traktor but, it’s limited to one’s creativity and knowledge of mapping. You’re right, there seemingly aren’t a lot of people embracing it for use with Traktor and there isn’t much info about it either. The Pioneer Traktor mapping is cool and fairly robust but, it’s not for everybody. You’d definitely want to get into mapping if you plan to use this controller, especially if you want to implement it’s velocity sensitivity. One drawback of the SP1 for me is, the lack of multiple LED colors on the pads.
I guess, for stems and loops, I would recommend the F1.. For hotcues, one-shots, tone play stuff, I would recommend the SP1. Honestly, with the way I like to play in Traktor, I couldn’t choose one or the other. I hope this info helps you determine what would be best for you.