I've owned a '11 touring S, I currently own a '14 pikes peak, and I've spent considerable time (about 1600mi on a 10 day tour) on a '15 touring S. I'd recommend getting a 15 over a 14 if the money isn't an issue, but if you can find a deal on a leftover 14 and want to wait a few years for issues to be sorted. A few notes about my years of multistrada ownership:
- Ignore any comments about the bike's "sub-3000rpm lack of performance". It's not an issue.
- The 2015 DVT 5k "dip" was not a noticeable issue for me during any time while riding it, and the DVT motor loves to be revved just as much as the previous gen motor, so you won't be lugging in the midrange anyway. If you hold dyno charts in high regard and carry them with you at all times while riding, then yes, the 5k "dip" may be an issue.
- Buy the bike from the closest dealer to you that has the best service department you can find - you will be getting to know them. I've been using Motor Cafe for service. I've had my '14 in for several warranty issues / TSBs, and they always fix it quickly and with no hassles, but it's still time spent bringing it in, getting a ride to/from, etc. My issues so far: front fork TSB repair, throttle cam TSB repair, DSS errors (twice) due to failed accelerometer and cable wear, leaking clutch master cyl, and the rear brake once or twice.
- Get used to the rear brake not working great on these bikes. The 15 DVT's rear is marginally better, but if you use rear brake, get used to it not being very powerful.
- Wind noise / buffeting is a fact of life with the stock touring / GT windscreens, for both the 10-14 and 15 DVT. The Pikes Peak shorty is better on buffeting but you still get a little bit. There's all kinds of fixes from huge alien-head screens with lip spoilers, to "wing deflectors" and other bolt-on windbreaks, but you can read the forums to try to find an acceptable setup. The PP CF shield works great for me, but it was not awesome on long distance touring days with cold wind and rain.
Again, highly recommend the 2015 DVT. The S1K XR is nice (esp. that shifter) but the DVT twin, while down on power to the XR's i4, has a much more menacing sound and the torque is heavenly. Oh, and the Skyhook 2.0 on the DVT is absolutely amazing. The '14 skyhook is pretty damn decent, but the DVT's is miles ahead.
Edit: I think the 2016 DVTs are available now, or soon? Might be able to find a leftover 15, too, or just get the new one.