I use Repti Glo 10.0 as thats what all the local reptile stores have around here in the UK. Its what ive always used. Ive not actually seen them stock anything else. Dragons you mentino Arcadia - do you get that from a rep store or pet/fish store ?
Also seems different stores tell you that they last different times. Some still say 6 months - others say 9-12. I change mine when i see a little black dot appear at one end, which is usually around the 9-10 months of useage.