no, not all mealies are the same size. i got some from petsmart that were pretty much big lookin' mealies that were similar in size (timberline), but the ones i got at petco were all totally different sizes... really small to kinda big (rainbow). mealworms molt 9-20 times in a month or so before pupating (look like aliens) and then turning into beetles (they lay about 250-1000 mealie eggs in 1 lifetime).
also, if your leo is still a baby, he might prefer the crix more because they seem to be a lot more active than mealies. wiggle the mealies around a little and make sure your leo sees it... after a while, they'll begin to realize that mealworms are food and would try 2 eat it... some leos are picky so it might be hard 2 get them on mealies
a couple times, my leo would look at sniff or lick then leave if she wasnt hungry - but she's into them now since its her staple diet 
good luck & take care! 
[aimEe]
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0.1.0 Albino Leopard Gecko (Marlene)
0.0.2 Fire Bellied Toads (Norman & Forman)
0.2.0 African Dwarf Frogs (Hobo & Bobo)
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1.0.0 Black Lab / Pit Bull (Mikey)
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