The most relevant comment (IMHO) I've seen here is that it depends on what you need the lens for (I use 'need' in the less precise 'photographer' context, given it's an Xmas present ;-)
The 24mm offers somewhat superior image quality, but if you want extra wide, then it has to be 17mm
I use both regularly for my paying work (architecture, interiors, industrial), but looking at my archive, 17mm use outstrips 24mm by around 3:1. My 'minimum' bag on a job typically has 17mm TS, 24mm TS and 24-70 on a 1Ds3
Filters are not an issue for me, I just don't use them. Then again I regularly use both TS lenses hand held...
I've just finished writing about the Samyang 24mm TS lens, which is nowhere near as poor as some would suggest.http://www.northlight-images.co.uk/reviews/lenses/samyang24ts.html
I should note that it's perhaps more written for those wanting to actually use the lens rather than pore over MTF charts and tables of measurements ;-)