I think we should go with two-stroke, as it is (slightly) more common. Also, (IMO) it flows a little better. The same would also go for 4-stroke and four-stroke, although which one is again completely aesthetics.
They are basically the same thing. IMHO, it should probably go under 2-stroke just because I think it looks better (complete aesthetics here - Really it doesn't matter). It definitely should be consolidated, either way. There is also 4-stroke and four-stroke ... either one could go either way. The real question is, since you brought it up, which way should it go? Edit your idea in your question and we'll tag @BobCross or @Movemorecommentslinktotop to come do the deed, since we don't have enough people in either tag to vote on making them a synonym.