The "Turbo Twist" is an easy one to change the bulb in it. If you consider this one, my husband was warning me about the "older version" with the double walled housing, he said they're not any good... but the newer ones are good. If you decide to go with this brand, let me know and I'll explain how to tell them apart.
You want to probably stay away from the Current USA UV Sterilizer. It uses a T5 bulb and is hard to get parts for. I've dealt with the owner of this company a few yrs back, I chewed him out pretty good for his advertising of a large number of fancy goldfish on his boxes... the goldfish were crammed into a small globe shaped tank and I had customers complain about it left and right. He laughed at me, said "any idiot knows that's just for show" even after I pointed out the number of dead goldfish customers our store had dealt with since his box appeared on our store shelves. He promised to send me parts for one of his tanks, I am still waiting for those parts yrs later. The guy is a cocky jerk who thinks his "****" doesn't stink.
Outside of that, pretty much most of the market is comparable to each other right now for UV units. Work with what your budget will allow, just make sure it's a unit that can handle a 200 gallon tank so you can use it when you upgrade to the bigger tank. For the turbo twist, 12X (36 watt unit) would be the one you want. While it may seem like overkill for a 55 to some, considering the fish we're dealing with and the for sure need to upgrade to the 200 soon enough, it's worth saving the money in having to buy another one later. It certainly won't hurt the 55!
Hope this helps!