I think for most tasks, you'll be ok with the cooling and Dell is #2 in customer support right behind Apple. I don't think you can do better from a customer support perspective - excluding apple
I was decided on a 15" (I currently own an older 13") up until this morning when I went into an Apple store. The 15" imo just looks too big for a laptop. If I was docking it and not carrying it around all day every day I'd go for it, maybe, but seeing them both together, the 13" just look and feels so much better.
Again, this is just my opinion. I ordered the 13" today, so hopefully, I won't have any regrets.