IMO, LED is becoming the best option. There is beginning to become more information about what is necessary, and the best for every setup out there. Just as there is for T5, MH, PC, etc. I personally am going to be doing a DIY kit from rapidled.com for my 10 gallon nano to test it out myself before upgrading my 75 gallon.
I hear that 48 LEDs are ideal for a 55 gallon, and they also work for 75 gallon tanks. I will try to find the best build thread that I have seen so far. It is a build somebody did for his 75 gallon, and he knows a lot about LEDs now, so you could ask him for more information.
Also keep in mind, yes LEDs are more expensive up front than anything else, but if you figure you have 4 T5 bulbs to replace every 12 months at about 25 bucks a piece, that is 80 dollars every year just for bulbs. And LEDs are supposed to last anywhere from 5-11 years. So if you spend say 500 bucks for 5 years of LED light, opposed to $100 for the fixture+ (100 for bulbs x 6 sets of bulbs = $600) = $700 for T5's for 5 years You save $200 in the long run. Not to mention the like 1/4 of the power you will use each month using LEDs over the T5s.
IMO LEDs are the way to go nowadays. And I said 6 sets of bulbs because the oddysea bulbs are junk I hear. And just me, I have read to many horror stories of Oddysea ballasts catching on fire.
Just my 2 cents
