I'm with Verizon for two reasons, and neither have to do with their service.
#1 - Their Share Everything plans allow phones from different area codes to be on one plan.
#2 - They will unlock iPhones so you can use pre-paid local SIMs when traveling internationally, even when still under contract.
Other than that, I am not impressed with them.
They were the first national carrier to offer LTE where I live (Virginia's largest metro area), bringing it here two years ago this month. Their LTE coverage then was nowhere near as strong as their voice/3G coverage, and over the last two years, the areas that got crap LTE signal still get crap LTE signal. Also, over the last two years data speeds have dropped from 10-15mpbs down to 3-5mpbs down. It's not unusual for my smartass roommate with an AT&T iPhone 4s to remind me that his "Faux G" HSPDA+ phone keeps up with mine in terms of data speed. i.e. he can refresh Facebook faster, load webpages faster, do IMDB lookups faster, ... it's irritating.
AT&T and Sprint both rolled out LTE here earlier
this year, 1.5 years
after Verizon. But both of their LTE networks seem to outperform Verizon's here in terms of coverage and speed, at least from what I've seen from my friends colleagues that have their service.
Hopefully Verizon's a different story in your neck of the woods!