RaShY - roshei teivot for Rabban shell Yisroel
Nevertheless, I have several reasons for preferring Tosafot's approach and essentially it comes in two flavours...
1. Tosafot bring down external sources thereby supplement a "Sugyah" with other sugyot or with non-textual sources
2. Tosafot are so transparent. Admittedly, some of their pilpul might be "Dochaq" but at least they are transparent about it. There is little in the way of a hidden agenda there.
Take it or leave it, Tosafot usually give you the HOW they get there along with the what.
IMHO it is easier using Tosafot to master dialectics than the Talmud itself - whose range of dialectic is far more complex