I think you're right about the Saturn being the most unique, although the Dreamcast does have its fair share of classics too. I really like Christmas Nights, it's a gem of a game for being only a demo, I even like Burning Rangers when I can be bothered with it. There's still a lot of games I want to sit down and play on that console, Clockwork Knight looks pretty fun, Dark Saviour, Shining the Holy Ark, Shining Force 3, Panzer Dragoon Saga, all games I have still yet to play. There's definitely life to be had from that console before you even consider the massive catalogue of Japanese games.
Both are great but I would say go for the Saturn for the exclusives. Most if not all of the great Dreamcast games by now have superior or at least comparable ports on newer consoles. Games like Three Dirty Dwarves, Saturn Bomberman, Panzer Dragoon Saga, or Astal make the Saturn for me. Many other good ones too but was trying to stick with console exclusives.
I don't know about that, a lot of the DC's library is enhanced PS ports. It's got the best versions of some great games, like the first two THPS games and RE 2 and 3
That's true - I think some people overlook that fact. It had quite a few games that also had PS1 and/or N64 versions, and the DC version was always the best. I would also say that a lot of the ports of Dreamcast games to other systems have been rather shitty. Most of them are about the same as the DC version or worse, so you might as well play the DC version. Plus, the Dreamcast had a much cleaner video output than, say, the PS2/GC/Xbox generation, so that's a reason to play the DC version over the ports for those systems.
Also Army men sarge's heroes was a Nintendo 64 port of the Dreamcast version with a few extra content & a "Making of" video from the Saffire Team developers
First i would "secure" a Dreamcast and then, in time, buy the Saturn. Both are must-have consoles. Don't worry about the PS2, they made a lot of them so will be very easy to get another one in the future. Both consoles have unique games (I personally avoid 3D games in Saturn, but that's something personal ).