In a recent game against a player rated in the mid-1600’s I arrived at this position as White. The first thing you notice is that Black is down the exchange. This was the result of having been caught in an opening trap. The game started out with 1.d4 d5 2.Nc3 Nf6 3.Bg5 but after 3…e6 4.e4 Be7 5.e5 Nfd7 6.Bxe7 Qxe7 7.f4 it’s now a French Defense. Now instead of 7...O-O Black played 7…c5? and after 8.Nb5 0–0 (Better was 8...Kd8 9.Nf3 f6 10.dxc5 fxe5 11.fxe5) 9.Nc7 Nb6 10.Nxa8 Nxa8 11.Nf3 Nc6 12.c3 Nb6 13.Bd3 cxd4 arriving at the following position where Black has lost the exchange and White must consider the sacrifice on h7. Is it sound?
If you look at the general criteria required for the sac to be successful as described in the post on the classic B sac, they are there so it looks as if the sacrifice is correct. Taking a look at the analysis you’ll see that it was not a forced mate and though Black had to thread his way through some tricky variations, his position was not without its resources.
What if material had been equal? Would that have affected the evaluation? Let’s replace Black’s R and White’s N in reasonable positions and look at the position:
Conclusion: Do not assume this sacrifice is an automatic win for White. Oh, by the way, that’s exactly what my opponent did in the game…he resigned when he saw 14.Bxh7+