I enjoy both games, and they're actually pretty different.
Escape's soundtrack really is just a timer, but it's some added fun anyway. I feel that Escape is a lot more chaotic and akin to a 90s TV game show, which I think makes it a better family game (you could easily convince someone it's a Legends of the Hidden Temple boardgame, complete with the crushing defeats). I think I've only played the base game, so the Big Box will include lots of options for variety and crazy twists.
Space Alert is practically a whole 'nother beast. For starters, the soundtrack is not just a timer, but a script that directs what happens in a game. It's a programming game, so you don't resolve "what actually happens" until the timer stops and you step through all the actions everybody did. Space Alert is a lot less chaotic and gives you a little more room to think and plan, but it requires more foresight, teamwork and delegation of responsibilities.