Depends on the setup, but the primary benefits of LEDs
- Cheaper to run, they use less power
- Never need to replace the bulbs (by never, I think it's estimated at 50,000hrs life)
- Bulbs don't fade/diminish over time
- They run cooler than T8, T5 and MH
- Smaller fixtures
I don't know how far advanced the LEDs are for a planted aquarium, but certainly for general non-planted they are fine, and for SW/Reef setups they are well advanced.
FWIW, I'm using a Finnex Ray II 18" LED fixture on my moderately planted 10 gallon and everything is growing like weeds. Only extra things I do are trim and dose flourish every couple of days.