It is not exact and depends on other skills and his heights but 1v1 for F trains about 0.2 and JS for F trains about 0.35. If you don't want much HA-DR, and you want only JS (if it is very behind) then you should train JS. But it also trains IS, keep that in mind :) I will train my forward young players 1v1 F, let's say it trained 4 JS 10 HA 12 DR 5 IS, then I will train JS F to complement the lack of JS and IS. It is not a bad training if you need more JS, but 1v1 forwards is definitely the most efficient trainig.