Hokkaido vs Japan Alps

Hello everybody
we are a group of four ppl traveling around 18 days to japan.
we wanna go to tokyo kyoto including some of the day trips over there. but why didn't decide yet if to go to hokkaido or to the japan alps, since we love nature and hiking. the thing is if we go to hokkaido it will makes it very hard to decide if to purchase the JR Pass or not.
i would like to know if we should go to the japan alps or hokkaido?

It really depends on the season. Japan is a country where the season plays a large part of where is peak season.

That said, Since you are traveling between Tokyo and Kyoto with the Japan Alps being between the two, it makes much sense to go to the Japan Alps.

If you wish to go to Hokkaido by train from tokyo, it takes half a day. (My friend did it) There are overnight trains that makes the transit much easier but these usually are booked out well in advance. Do check in regardless. Due to time and much else, i recommend flying to Hokkaido. If you use ANA Japan experience, you can fly from Osaka Airport to Sapporo Airpot for 10,000 yen.

However, all in all, I think that Hokkaido needs a good 5 to 8 days. With Tokyo and Kyoto too, it is really tough to fit everything in. Japan Alps on the other hand is really large, and no one plans to complete it in one trip. Since it is SO LARGE, and is Easily Accessible. Being near Tokyo, Nagoya and other major cities/international airpots.

Once you decide maybe, you can make another posts and we can help you plan the sights and sounds. Also, remember the posts the month. As said, season is important.

Thanks a lot Joshua Hugh
i forgot to mention that we will be in japan between 23/09-15/10
and if we decide to go to Hokkaido by air, then having a JR Pass maybe isn't a good option ?!
because it feels like if we choose the japan alps then we will have the JR pass but if we choose hokkaido we are not sure about having the JRpass and that's another decision we are struggling with
any advices?