I love Leander (so it's getting my vote), but at the same time I'll admit its shortcomings.
As has already been mentioned, it features some massive indistinct maps, which makes getting lost all too easy. The biggest issue I've found with the game are that it has too many "leaps of faith", where you're required to jump into a void, which may have a platform for you to land on, or it may have a row of instant-death spikes. There's far to much of this in Leander.
I think I'll have to give Assassin a go this weekend. I've not played it for years.