Depends what's in the kit. Shoot Mike an email and ask him what the differences are.
Soffseal is fairly decent for aftermarket, but can be a bit unforgiving for door seal ends and allowing the door to shut easily. At least on Oldsmobiles. And I heard montes are about the same.
If you want to spend a bit of $$, Steele has some really awesome reproduction seals for the door and roof rails and the trunk seal. At least from the reviews of others I've seen. They're pricey, but they sure look close enough to GM stuff that I've seen. I cannot verify fit, etc., as I have never personally owned any. I use GM stuff where all possible. I gave SoffSeal a chance on my 84
H/O but I couldn't close the doors and I got tired of "fixing" the seal ends. So I put GM seals on the doors. Problem solved. This was about 20 years ago, so if SoffSeal got better at it since then, then fine. I've read where they still seem to be about the same. Correct me if I'm wrong.
I have found NOTHING beats OEM GM seals if they're not dried out and cracked. But obviously, far and few between. For the trunk, you can buy a new GM part for just a tad more than the Steele part. Search 20111565, 20469449, 20490800.
People can restore as they wish and it's their budget, but I can tell you this, when it comes to weatherstripping, you really do get what you pay for.