Is there enough room in his new enclosure to put the new bigger hide next to the old smaller one? If so, put them both in and let him decide which one he wants
If not then my vote is go with the bigger one so he can get into it when he's full which is when he'd want to be in there the most.
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Slytherin Serpents
Have you been hugged by your snake today? 
Ball Pythons
1.1 Het Caramels (Edward & Bella)
0.1 Normal 66% ph Caramel (Rosalie)
1.1 Caramels (Crookshanks & Bellatrix)
1.0 Honey Bee (Aragog)
0.1 Hypo Pastel (Nagini)
0.1 Spider 66% ph Hypo(Nymphadora)
1.0 Mojave (Lucius)
1.1 Pastel Lessers (Jacob & Narcissa)
0.1 Pinstripe (Arwen)
1.0 Pewter (Salazar)
0.1 Bumble Bee (Alice)
1.0 Bell Pastel (Jasper)
0.1 African Dinker (Esme)
0.1 Het Pied
0.1 Hypo Cinny (Myrtle)
1.0 Cinny het Hypo poss het Albino
1.1 Pastel Dinkers (Snape & Xiomara)
0.2 Ghana Dinker Babies
0.0.3 CH Dinker Babies
Corns
1.1 Normals het Amel, Anery, Charcoal, Diffused, Hypo (Romeo & Juliet)
1.0 Blizzard het Diffused (Tumnus)
1.0 Blizzard poss het Anery, Hypo, Diffused (Cotton)
0.1 Anery Lavender het Amel (Lucy)
0.1 Plasma poss het Hypo (Victoria)
1.0 Plasma poss het Albino
1.0 Hypo Plasma
1.1 Amel Motleys (Harry & Ginny)
0.1 Lavender Motley poss het diffused
1.0 Lavender Pinstripe Motley het Amel
0.1 Fire poss het Anery, Charcoal, Hypo (LeeLoo)
0.1 Normal het Albino, Lavender, Anery, Charcoal, poss het Diffused
1.0 Albino het Lavender, Anery, Charcoal, poss het Diffused
1.1 Sunkissed poss het Plasma (Arthur & Molly)
0.1 Dilute Blue Motley (Myrtle)
1.0 Pastel Motley (Nick)
0.1 Diffused Caramel
1.0 Blizzard 66% poss het Diffused
1.0 Pewter het Albino
0.1 Fire het Charcoal
Thayeri Kings
0.1 Leonis phase (Sidney)
1.0 Milk Snake phase
Milks
1.1 Tangerine Albino Hondurans
0.1 Hypo Tangerine Albino Honduran