I think Dubias will be healthier in the long term. Esp. if you keep them for a few weeks at a time and are in charge of feeding the Dubias. They can easily be housed, fed well, gut loaded, etc. I also like that they don't stink like crickets, don't die as fast and don't chew on your animal.
They move slower so perhaps it won't make your little one as nuts to every jump.and movement. On the other hand..they really tune in to quick movement. I don't think you should have to much issues switching. Just do it sooner then later before your little ones becomes to hooked on crickets.
Many people feed crickets so it's not a bad thing. Just try to gut load them for a couple days before feeding and dust them well. Make sure you don't have loose ones in the enclosure that you will have to hunt and get out before they chew on Crestie. Keep having to dig around in the cage to the minimum. Like cleaning and getting Crestie for handling.
If the new cage is almost the same size anyway, you could go for it. That is really big though. When you set it up make sure you have it the way you like it so you don't make so many changes again. Put something familiar in there. Like a favorite plant or hiding spot. Make sure you can easily do maintenance.
Good luck
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