I don't think those 2 really compare - it really depends on your usage. If money is not an issue and *weight* is not an issue, Studio hands down. If weight *is* an issue, then SP8 because you can then use in tablet mode without the extra weight of Studio's base.
I myself wouldn't get a Surface Pro anymore though, just because you eventually have to replace that keyboard, and I don't mind the weight - so Surface Studio all the way.