You can use both and I don't see any difference in meaning. I think the first is a bit more colloquial.

I consider the omission of the anticipated 'it' after 'Like/Love/Hate/Enjoy' followed by a 'when' clause to be a degredation of English language, brought about and perpetuated by internet memes. As a purist, my thoughts run as follows: In omitting the anticipatory "it", you are missing the direct object (Not the complement, since the real direct complement is the clause "when when you smile at me". ) In our case, 'like' is also a transitive verb and so we cannot say 'I like.' and leave it at that. Consider the song: I like it, I like it! I like the way you run your fingers through my hair And I like the way you tickle my chin And I like the way you let me come in ....... Gerry and the Pacemakers. Could they have sung: I like, I like!'? No. Nor can we introduce 'it' before infinitives, only after them. Consider: I like to move it, move it! I like to move it, move it! I like to move it, move it! I like to MOVE IT! I note with interest M. Swan's take on this - in particular notes 'g' and 'h' We use the anticipatory or preparatory it when the object of a verb is an infinitive expression (in particular after Like/Love/Hate) or a clause with an adjective or noun complement: a. I find it difficult to talk to you. b. My blister made it a problem of walk. c. George made it clear what he wanted. Note that this structure is not normally used when there is no adjective or noun complement after the verb: e. I cannot bear to see people crying. f. I remember that they were very happy. But note the structure I like/love/hate it when... g. I love it when you sing. Note also the idiom I take it that.... (=I assume that....) h. I take it that you won't be working tomorrow From Swan, M. (1995) Practical English Usage. OUP So, they way I see it, and the way it should be seen (no to make to fine a point of it) It it simply Wrong to omit the 'it' after 'I like' followed by a 'when' clause. So, if we could all stop doing so, please?

They are both the same to me. I find 'I like when ...' to be the more casual form, and something I'd hear more in conversation when native speakers are more like to drop words ('it', here) for speed and brevity.