I can give a quick rundown of all the upgrade perks, though I might miss something. But I'll try my best. My premium actually rvplitee this morning, so this is just what I remember as well as some rewording of the game guide. If you need any clarifications just let me know. ^^
Wolf Perks (stuff you can do with your wolf):
Private sales/breedings - You can put a wolf up for one specific person to buy/breed to, so others cannot "steal" the wolf or breeding.
Play - After going exploring, you can go to your wolf's page and there will be an option to play with them. By playing, you may or may not earn a play point (the likelihood of earning a play point depends on your wolf's playfulness level). Once a wolf earns 25 play points, it can be transferred into 25 CP.
Pack Activities perks (these can all be found under Pack Activities):
Breeders Report- An extra tab found on the Reports page. It gives you a list of all your females that are currently pregnant and how long they've been pregnant for, the pups that your females have had recently and which wolves sired them, and how much mush each of your males have made you from being bred to.
Explore teams - You can create teams of wolves to explore with, so that when you go to explore you can simply select a team instead of choosing wolves to explore with individually.
Specializations - You can complete certain goals in one of four categories. Once you complete those goals, you'll earn special rewards such as increased chances for talents, extra den space, etc. (I don't remember much about these, apologies)
Roleplay perks (can be found under the Roleplay Tab)
Stories - This is meant for players to post their roleplays for others to read, but you can also post your own stories here, as it has a nice chapter by chapter format.
RP With Me - If you're searching for someone to do a certain type of RP with you, you can post your ads with what you're looking for here, and it'll be displayed on the RP With Me page for everyone to see.
Other perks:
You get 40 CP every day instead of 30.
You can explore every half an hour instead of every hour after running out of moves.
You can have banners, which are displayed at the top of your den and as signatures in the forums.
You can play Border Patrol every hour instead of every 24 hours.
<div align="left">You can have multiple saved mail folders (PMs in these folders won't automatically delete)