The tube uv is definitely better, coil ones concentrate the uv more and have sometimes caused eye problems. reptisun or reptiglo 5.0 are the best, but need replacing every 6 months or so (even if it looks ok, the quality of light goes down fast after this point).
Also, do you have a male or female? A tube uv would be easier to transfer to a bigger cage if you are planning on getting an 'adult' sized cage in future.......maybe it would be best to change it all now?