The first problem with the second version is the intransitive use of show. This may occur, and it may be possible to argue its grammaticality, but it is not, I suspect, widespread. Many readers will expect has been shown, and there is no reason to disappoint them.
The second problem is the use of however as a coordinator. This is becoming more frequent, but it is not yet universally accepted. It would therefore be advisable to change it for but or to use it to start a new sentence or to put a semi-colon rather than a comma after dataset, as in the first version.
Thirdly, the absence of the indefinite article before significant performance gain is a little unusual, but not necessarily ungrammatical. When used to make a generic reference the zero article (that is, no article) is normally used with plural and uncountable nouns. Gain is generally a countable noun, but I can just about see it as uncountable in your sentence. However, the absence of a, like the intransitive use of show, might stop some readers in their tracks, so on pragmatic, if no other, grounds, it might be as well to use it.