Generally speaking, the fractional rig will have a smaller headsail, which is easier to tack and the mainsail will be larger than the masthead relatively speaking. On a masthead rig you can expect most of your horse power to be off the headsail, while on a fractional rig, you can expect your mainsail to be very important in the horsepower area. If you sail in very windy conditions, you will like the fractional rig because the headsail is easier to tack, the combined center of effort most likely will be lower and the mast will probably be tapered, which means it will bend to leeward in a blow, which helps depower the rig for better control in higher winds. If you have a masthead rig, you will have very big headsails, which might be better if you sail in a very light winded area. You will like the additional sail area and the higher combined center of effort the masthead rig will offer. You usually have more bend control over a fractional rig for various shapes in various wind conditions. Many masthead rigs are like telephone poles and do not bend much.
The Ericson 30+ is a faster boat than the Ericson 30. It has a different keel, probably a longer mast and I just happen to know it is a pretty nice sailing and fast boat (powerful), which will have a fun factor that the E-30 does not necessarily have. Also, I believe the interior of the 30+ is fancier and perhaps more pleasing.
So, it might depend on how many people you are sailing with, where you sail and what sort of wind conditions you have, how you are going to use the boat (if you are ever going to race it, go with the 30+) and then compare the basement to see what sort of cruising accommodations each have.