I really wouldn't mix on-site warranty with mail-in warranties, they are WORLDS apart. With mail-in warranties, it's like a black box, you have no clue what was done or where it was done. I've had my laptop long ago(MSI) lost for over a month with no one having any clue what was going on only to be contacted later if I wanted to do fix A for extra money or default fix for no extra cost. It can get even worse when you have to pay part of the shipping which is effectively them holding your laptop hostage.

In comparison, on-site warranty is a lot easier because you don't need to do with hassle of shipping, they fix it in front of you so you can see if the damaged something while taking it apart. You can also test the laptop before  accepting the fix. You can communicate with the person involved to be sure he understands your issue and it is not "lost in translation". And best of all, 9/10 you can have them fix things that are generally not covered by warranty. I've had onsite warranty fix things from cosmetic damage to replacing batteries (which often have 6 month warranties or separate warranties) but you can easily get them to replace your battery.

So the on-site experience and the mailing experience or walk into store experience is worlds apart.

Also, many manufacturers have tiers of support, I don't know if it is still the case, but Dell XPS used to have separate support from non-XPS which was much much better then your latitude or insperon support.