From what I can gather so far Dawn is a "sequel" to Aria on the GBA, and if I am reading things right, they have Rondo/SoTN like gameplay. Anyone else know if this is right?
That's right. You're in a huge, interconnected castle that you explore just like in SotN. In this game, when enemies die there's a chance they'll drop their soul, which gives you either an attack, a passive ability or an ability of some sort. You can equip three of them, one of each type, at a time.
Portrait has you changing through casts members to solve puzzles and areas.
PoR has two protagonists, Johnathan and Charlotte. They say the other person's name every time you switch characters, so expect to hear a lot of CHARLOTTE JOHNATHAN CHARLOTTE JOHNATHAN CHARLOTTE. Johnathan uses the Vampire Killer (badly) and can learn some sweet moves. Charlotte is a witch that can learn a few different spells. Again, this is one big map that you explore like SotN.
Ecclesia doesn't have a Belmont and it uses some sort of Glyph system for weapons.
Ecclesia's MC is Shanoa, who is awesome. Instead of enemy souls she gets glyphs, but it's fairly similar. I like that she can dual wield different weapons. The game structure changes in this one: there are different locations to visit, each with their own smaller map. Shanoa can find items inside treasure chests, and there are special ones that respawn when you revisit a map that have a chance to drop important weapons and armor, making you farm them out a bit. This game is like the link between the other Metroidvanias and the XBLA free-for-all grindfest.
I liked all three but OoE was my favorite. Shanoa is awesome and the game is actually somewhat difficult.