Roland HPD 15 vs HPD 20, witch one is better?

Hi, im new in this forum and would like to hear some opinions in witch one of this Roland guys is better, the HPD 15 or the 20? I wanna buy one of those but not always the new version is the best ( or is ?)
If anyone has some input in those guys please give some advice

Take care everyone
Rick

You can check out a review of the HPD-20 in the Nov 2013 digitalDrummer e-zine via this link: http://issuu.com/digitaldrummer/docs/digitaldrummer_november_2013_lr?e=1761416/5719134

Also here is an index of all their reviews listed @ vdrums, including the HPD-10 and other mutipads: http://www.vdrums.com/forum/forum/general/products/61129-digitaldrummer-review-index