Some things you can do with 1.7 but not BSM:
Sprint mid-air. If you're falling from a giant tower but forgot to sprint, you can still hit the sprint key while mid-air and start sprinting before you hit land. With BSM, you need to be touching the ground before you can sprint. (Also if someone hit you and you're midair you can sprint if you time it right
Sprint while swimming. Before, you had to touch the ocean floor to sprint, but now you can do it at any time in water.
However, BSM also has some advantages that can be used in any old multiplayer server (Unless it's banned, like on MCG)
You can press a key once, and whenever you press W it auto-sprints. It can be disabled by pressing the hotkey again.
A bunch of others, but there's mosquitoes biting me so BYEE