These mid-tier ethergaunts, notable for actually wearing clothes, have 11 HD. They're very comparable to the reds: Stupefying gaze, Enslave, Total Vision and Material Jaunt are all unchanged. Constitution, dexterity, and intelligence have gone up at the cost of two points of strength, and Combat Casting isn't a bonus feat anymore (but still something the default monster has chosen, apparently).
White ethergaunts' Spell Immunity has been upgraded to cover 3rd- and 4th-level spells, and their casting is now that of a 13th-level wizard, making a LA of +2 the bare minimum. To balance out the many other goodies the 'gaunt gets, I think +3 or +4 is more appropriate, though.
A LA of +5 is honestly reasonable here. Being behind on casting a bit is compensated for more than adequately with the great stats and special abilities.
16 RHD, 17th-level casting, better stats (including a whopping 31 intelligence), and 6th-level Spell Immunity (now covering spells like Flesh to Stone, Feeblemind, and Baleful Polymorph). Not a lot worth mentioning here that hasn't been discussed in some other entry already.
When you consider the giant intelligence bonus, a black ethergaunt isn't that far behind on casting compared to a 20th-level wizard, and as such I'm comfortable assigning it +4 LA. Class levels aren't that important if you have 9th-level spells.