the benefit is going to be more in how many bulbs you purchase at a time if your cfl's are oriented correctly and reflected well. using the light efficiently is where most folks get lost, imo. if they are oriented downward and reflected in a polished dome they should be more than enough. couple that together with the fact that they're fairly inexpensive and available in multi-packs everywhere and there's not much savings and you're in the hole for a fairly expensive fixture if you go with t5ho. the downside... cfl's seem to have to be replaced more often to produce decent light... and finding the right fixture/reflector.
lumens themselves will be almost identical per watt. the gases/phosphors will determine the colors, so given the same gases and lumens, they're essentially the same bulbs. just one's twisted and has a built in starter.