Even if it isn't fluted, 2 extra inches of barrel won't make much difference in weight.
I have Encore rifle barrels in 24, 26 and 28 inch lengths and, given the choice you were given, I would go with the Prohunter 28 inch barrel.
I don't know about availability but you might also consider a non custom shop barrel. I have a couple of tapered 24 inchers with iron sights that I like. All you do is put a Warne Maxima base on the barrel and use Warne QD rings and if you ever need the irons, you can easily take the scope off to do so or switch scopes between barrels. I've found the accuracy from the tapered, heavy and Prohunter barrels to be pretty good in all.