Is it correct to say more than what meets the eye? More than meets the eye sounds incorrect, but I've seen a lot of people use it and that confuses me. What acts like an object to the phrase which otherwise seems incomplete.
Both options are perfectly acceptable. One is a noun-phrase (NP) complement of than and the other is a comparative-clause complement. They are structurally equivalent to
In , a budget cut is an NP complement of than. Similarly, what meets the eye is also an NP complement of than.
(That's all you need to know about that construction, but if you want to unpack it a bit more, what meets the eye is like the thing that meets the eye. This is an NP with thing as its head and a relative clause functioning as a modifier. In the case of what meets the eye, the head and the relative are fused: the pronoun what functions both as the head of the NP and the subject in a modifying relative clause.)
The other option is there is more than meets the eye. In this case, meets the eye is a standard comparative clause functioning as complement of than. A comparative clause is different from a main clause in that it typically has a gap (e.g., I'm bigger than [she is _], in which the adjective big is gapped out.) The gap in your sentence is in the subject position (i.e., there is more than [_ meets the eye]) and could be filled by the NP the budget cut, for example, if it were a main clause.
Both are grammatical, as others have said. But to me
is a perfectly normal expression, while
is something I never recall having heard, and I find it odd — but just because it goes against an established phrase, not for any other reason.
Compare "The book I wrote" with "The book that I wrote".
This belongs to the same category, where the demonstrative pronoun can be dropped with no loss in meaning. On the contrary, a gain in elegance (simplicity) is achieved.
"More than that, which1 meets the eye" lacks the simple elegance of "More than meets the eye".
Kind of like waiting on the bus as opposed to waiting for the bus. Where, in both cases, the bus is yet to arrive.
But I'll allow that what may in fact be a suitable alternative standard.
1: Standard modern English would prefer that, which to what in this case. More than what meets the eye sounds like a regionalism to me.