I know some of you may have different battery needs, but I recently replaced the battery in my 2014 transit connect, which I just use for daily driving. Old battery died suddenly, 0v across terminals, so it was probably an internal short. I ended up going with a genuine motorcraft from the ford dealer, part number “BXT 40 R”. This is their “100 month warranty” battery and they were able to do it for $120 + tax, (+reimbursed $15 core deposit.)
I don’t think there are any readily available AGM batteries that fit very well in the original spot - went through the same drill on the 2001 focus which actually use the same battery, none available like they are for other cars, due to the dimension/configuration. I got an interstate battery for that car at Costco which would fit perfect in the transit connect, but I don’t think it cost any less or is necessarily any better in quality than the genuine Ford battery I just got.
Accessing the battery on the transit connect was a bit of a pain, as I learned that basically completely removing the air cleaner assembly was necessary to get it to slide forward and out. And oh, was that air filter dirty, so I changed that too while I was in there. (Probably need to put some routine maintenance for this car on the list - recent acquisition but with about 110k miles on the clock.)
So far, it’s been a good car. Most of the issues I’ve had on it related to aftermarket equipment installed by the previous owner. But as far as the battery goes, think maybe the original, 2013-manufactured battery had just expired after ~5 years of use.