I have both, typically the leo will come out to see what is going on if there is a lot of traffic by the tank. You have to consiter that both leos and fatties are nocturnal and will sleep most of the daytime. Leos tend to be more to look at as well since they have such a varity of colors, but has stated before fatties put on more of a show during feedings. Lastly, leos are a cheaper purchase initally. I got my leo for $20 at Petco last year and my fattie for about $60 in an old fish store about 7 or 8 years ago.
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1.0 African Fat-tailed Gecko (Mike)
0.1 Leopard Gecko (super hypo tang - Autumn)
1.1 Red Ear Slider (Dirk The Daring and Iria)
2.0 Cats (Scruffy and Sonic)
3.7 Dogs (husky mutts ; one wolf/german shepard hybred)
Salt and Fresh water fish