Regardless of whether it's fluorescent or LED, the kind of light you want for plants is full spectrum or daylight with RGB accents. With LED, I actually honestly don't know to what extent wattage plays since LEDs as a rule emit low wattage but still have a very bright light.
If you want to get an LED fixture, I would suggest getting one that advertises itself as specifically for planted tanks or having features for planted tanks. That way, you are most likely to be getting bright enough light for low to medium light plants.
I use a Marineland Planted Aquarium fixture but I would not recommend it because it's very expensive and the housing gets crazy hot (seriously, it's LED and I thought those were supposed to be cooler-running!). I only got it because I really needed the built-in timer feature as I had nowhere to plug in a timer.
I actually really recommend this for an LED planted fixture:
[ame=http://www.amazon.com/gp/product/B007URFALU/ref=s9_hps_bw_g199_ir02]Amazon.com: Finnex Ray2 Aquarium LED Daylight, 18-Inch: Pet Supplies[/ame]
It's not too expensive as LEDS go and has the requirements needed for a planted tank.
Fluval has some new LEDs out too that may be worth looking into.
[ame=http://www.amazon.com/Fluval-Daylight-Aqualife-Aquarium-Adjustable/dp/B00BFUJUIW/ref=sr_1_5?s=pet-supplies&ie=UTF8&qid=1380088080&sr=1-5&keywords=fluval+led]Amazon.com: Fluval Daylight Aqualife & Plant LED Aquarium Lamp, Adjustable from 24" to 34" Length: Pet Supplies[/ame]