Ah, but consider this: as FPSSJ's, no normal Saiyan can beat them, regardless of skill, one-on-one, regardless of skill. So there are three very different scenario's they're expected to deal with:
1) Multiple weaker enemies, likely from a rebellion.
2) A rogue FPSSJ appears.
3) Powerful enemies invading the planet.
And three can be divided into two: dealing with the issue by themselves, or as part of a group.
Tien-style, being balanced, lacking in weaknesses and having techniques useful for all three scenario's, is thus a good choice, as there's no risk of being placed in a situation that the style is unsuited for. Piccolo-style would also likely be a good choice, but Tien-style's ability to increase power through sacrifice of life force, while being less reliant on battlefield control gives it the edge.