14w NO flourescent vs 10w CF?

One advantage to the CF is it is a cooler running bulb and is more energy efficient, but then, Betta's like a little heat. The plants you are using are low light type, so 10W would be plenty for the 5.5G. Also, in this size tank the 10W might be sufficient for the grassy foreground carpet, because the light will not have to penetrate much to get to the plants in a smaller tank.

In a smaller tank and depending on the specific plant you choose, such as micro-sword grass which requires moderate light, that plant will do better than Riccia, which requires high light. Your lighting at 10W will produce 1.8W of light per gallon in the 5.5 gallon tank. Cryptocoryne's will do well also. The benefit of a lower light tank is that the plants will grow slower and won't get out of control so easily.

Or you could make a carpet out of java moss. I'm doing this at the moment in my 5 gallon hex with a 10 watt CF. I just tie the moss with thread to a slab of slate and let it grow. I already have it growing this way in my 10 gallon and it gives a nice effect. Kind of looks like a shag rug type foreground. You could also use needlepoint grids if you don't have slate available.