Michael Howe raised a valid point for all variants that do not have a set of 'perfect promotion choices.' In FIDE chess, there is the common situation in King-and-Pawn endings where promotion to a Queen stalemates and promotion to a Rook does not - but a master will probably have resigned before this happens on the board. Also, sometimes you need to promote to a Knight and give check. For example:
45. Ra6 f1=N+ 46. Ke2 Rxd2+ 47. Kxf1 Rxc2 1/2-1/2 Promoting to a Knight (with check) on move 45 was the only way to avoid losing, according to my computer.
Michael Howe raised a valid point for all variants that do not have a set of 'perfect promotion choices.' In FIDE chess, there is the common situation in King-and-Pawn endings where promotion to a Queen stalemates and promotion to a Rook does not - but a master will probably have resigned before this happens on the board. Also, sometimes you need to promote to a Knight and give check. For example:
H. Reinle - M. Lange (Murnau 1936)
1. e4 e5 2. f4 f5 3. exf5 e4 4. Qh5+ g6 5. fxg6 h6 6. g7+ Ke7 7. Qe5+ Kf7 8. gxh8=N# 1-0 is a checkmate underpromotion.
Another example: J. Levin - A. E. Santasiere (Pittsburgh 1946)
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Na5 6. Bb5+ c6 7. dxc6 bxc6 8. Be2 h6 9. Nf3 e4 10. Ne5 Qc7 11. f4 Bc5 12. c3 Nb7 13. Qa4 O-O 14. Qxc6 Qxc6 15. Nxc6 Re8 16. b4 Bb6 17. Na3 Nd6 18. Nc2 Nd5 19. c4 Nxf4 20. c5 Nxe2 21. Kxe2 Bg4+ 22. Kf1 Bc7 23. cxd6 Bxd6 24. Na5 Bd7 25. Bb2 Ba4 26. Nb3 f5 27. g3 g5 28. Kg2 f4 29. gxf4 gxf4 30. Rhg1 Kf8 31. Kf2 Be7 32. Bg7+ Kf7 33. Bxh6 Bh4+ 34. Ke2 f3+ 35. Ke3 Rad8 36. Rg7+ Kf6 37. Rag1 Bxb3 38. axb3 Ke5 39. Bf4+ Kf6 40. Bg5+ Bxg5+ 41. R1xg5 f2 42. R5g6+ Kf5 43. Rg5+ Kf6 44. R5g6+ Ke5
45. Ra6 f1=N+ 46. Ke2 Rxd2+ 47. Kxf1 Rxc2 1/2-1/2 Promoting to a Knight (with check) on move 45 was the only way to avoid losing, according to my computer.