Best explanation on A2SD vs A2SD+ that I've read so far:
A2SD+ Lives quite Happily with FroyoA2SD.
You can use the A2SD+ ROM just fine even without a partitioned SD card. The A2SD section of the kernel will now simply go "Hey, there isn't an SDEXT partition. oh well. fat lot of good I am, then!" and then let Froyo handle it.
FroyoA2SD Installs Apps to the Phone's NAND by default. Apps have to be specifically CODED to allow to be moved to the SD Card. ModInstallLocation Can override this, and allow all apps to be force-installed to FroyoA2SD. HOWEVER, apps with Widgets will break if you plug the phone in for data transfer, as it mounts the SD card, and then bad stuff happens to the phone.

A2SD+ Fixes this issue, as the card remains mounted On Both the PC AND the phone, the Fat32 partition being unmounted for PC use, and SDEXT remaining mounted on the card. this DOES however, slow the card down. which is why it's reccomended to get a High Class SD Card (The reccommended is Class6, but they are very expensive) to compensate for the slowdown.
XDA Source