I'd also go with the dealer... not even knowing who did your suspension.
I've had issues with a business many years ago and the two owners got into a personal scrap... Thus affecting customer service. When one of them contacted me to appoligize and COMPLETELY RE-DO my front end, at his expense, I knew where to take my business from then on. Many weeks later, the other owner tried to get is old clients back... From that day on, the service the first owner gave, got him his business from many others and I.
So yes, principals apply here and so does customer service. A $1000 job vs a $80 to not claim responsibility on his job (even if it's not is) I find that low and unprofessional.
Go with the dealer, that is willing to put it under warranty, or else he wouldn't do it for free I guess!!!
Loyalty goes a very long way and if this suspension guy of yours doesn't value that, then take your business else where. I'll even give you the guys that worked and will work again shortly on my suspensions...