Solrwind,
It's already been repeatedly said in the half-dozen threads you've started, but:
Corns need a warm side of thier enclosure that has an available temp of about 84 F.
Corns need a cool side of thier enclosure that is somewhere in the 70s F range.
So if your "friend" can provide a temp gradient in thier enclosure without the use of external heat source then more power to him (and he must be some kind of magician).
As to the type:
Corns are nocturnal in nature -- they prefer to remain hidden away from lighted areas.
They prefer to have a heat source that comes up from below them, ie "Belly Heat", which is what they find in thier hiding spots and burrows in nature.
Are heating lamps acceptable? Yes.
Are heating lamps optimal? No.
And really, the price differential is so small [in the long run it actually shifts in favor of the UTH], why not give your animals what is optimal for them rather than just what is acceptable.
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PS: on a side note. I've been reading your threads all day long. In every one of them, you are projecting a seriously confrontational "attitude". It may unintentional (or may not be, I don't know), but it definately reads that way.