ARC LS 17 vs LS 25 Mk II

I'm looking for a new preamp and am seriously thinking of going with Audio Research. Given that these two pieces are very close in price, which do you think I should go for, the newer 17 or the upper level 25 MkII which is a bit older? I'm looking for good air, soundstage, transparency and decay.
If you want air, transparency and decay, the LS17 will win in those areas. The LS25mkII has more weight and slam though.

I'm an ARC dealer.
No contest,it's like comparing a Miata/LS 17 with a Corvette/LS 25.O.K maybe I embellished a tad.
Thanks Mark and Dave. So am I correct in saying that the LS17 sounds more refined, whereas the LS25 mkII has more low end authority? Damn, I wanted both :)
I had a 25MKII, now upgrading to REF 2MKII, it's a one of BETTER preams heard.
I've owned at least 5 different ARC preamps at one time or another and liked them all. You're going to get both refined and authoritive sound with the LS-25 MKII.I believe that's what the other poster's analogy between the two cars was conveying. The only reason I'm going to get rid of mine is to get a Ref 3.
I disagree with some of the opinions here about the LS25MKII. I demo'd an LS 25MKII and did not like it at sounds very transistor. I purchased a LS26...but would have purchased a LS17 if my budget wouldn't have allowed the LS26. I've heard the LS17 and it provides 70% of the LS26 performance. In my opinion, the LS 25MKII was not even in the ballpark of performance with the newer ARC preamps (in my system), including the LS17.

However, the best judge of all: your own ears. Try to demo both. I demo'd the LS25MKII less than a year ago and there should be a fair amount of these still at dealers. Call around.