You can see it for yourself right on the CP site, but just in case, here’s a brief overview.
CP is offering a set amount of coins depending on which membership option you chose: monthly, half-yearly, or yearly. Neither membership option is better, in many cases monthly pays off in the long run, but basically the longer you subscribe the more coins you get.
Membership allows you to own clothes and furniture as well. This is a big perk because you can dress your penguin and design your own igloo, as well as enjoy the free stuff that CP releases on occasion (for example: free Santa hats at Christmas time). Possibilities are endless with this perk.
Being a member allows you to be able to become a moderator, tour guide, and ninja. According to CP, the “secret agency” should not be disclosed, but since the recent incident, it has been exposed. You must be a member to become any and all of these things.
As a member you are allowed to own up to 18 puffles, which, if I remember correctly, is relatively 16 more than you can own as a basic player.
As a member, you can get into rooms faster than regular players. You are also allowed to give other players access to your igloo by adding your igloo to the map (otherwise known as unlocking your doors).
Basically, membership is worth it no matter what you pay as long as you’re active on the site. So become a member and enjoy your penguin life!