Contrary to popular belief, having hard shoulder caps is not an indicator of protection. Playing contact hockey would be better served by having a soft shoulder cap, or, if you can't get that, a cap that's as low-profile as you can.
What are your preferences for fit? Some fit bulkier so if you want hands-down the beefiest protection, there are pads for that. If you want a slimmer, more tight-fitting pad, there are options for that and finally, if you want a very mobile and lightweight pad, there are options for that too.
A lot of it is personal preference and comfort so your best bet to obviously try on a few yourself, but if you can tell us some of your preferences, we can give you a few starting points.
You want soft shoulder caps because it's safer for the opponent. Hard caps might contribute to concussions. I wouldn't be surprised if safe caps were mandatory in checking leagues.
The rest of the shoulder pad is personal preference. Some guys like a pad that just provides the bare minimum coverage (like Sherwoods which are used by some guys in the NHL that are WAY tougher than any of us) and others like shoulder pads with lots of spine, chest, and torso coverage.
in my personal opinion the pad that fits you best will be the most protective for checking. I agree with the above posters regarding hard vs soft caps as well.
My son recently bruised some ribs with his 3 year old pair of vapor XVI's. They were good but I knew they weren't the best. And no pads will protect where he got hurt (under the arm above the kidney). Still I went out and got him the best fitting pad. Sure there were more expensive and bulkier pads but we went with 9k's as they stayed in place and still gave him the mobility he likes.