Buying New Phone via T-Mobile's EIP vs. New-ish Phone off Swappa?

Hello all,

 

I'm in need of a phone upgrade, as my trustworthy HTC Sensation 4G that has dutifully served me for the past 4 years seems to be too slow. After much extensive research, I've decided that the LG G4 will be my phone's worthy successor. I've gone in store to try it out and I feel that it's more than adequate for my uses.

My question is about whether to purchase the phone on T-Mobile's monthly payment plan or to buy a like-new phone off a 3rd party. T-Mobile's price is $600, whereas I can likely pick up a like-new one in the range of $490-520 off Swappa.

I don't need JUMP as I plan on having this phone for a while, nor do I need PHP. If I were to switch phones, I would want to just sell it, but I wouldn't do it so frequently such that JUMP would be a viable option. I also understand T-Mobile and LG offer some promos like an extra battery and back cover if I purchase one from them, but I believe I can also redeem those using the IMEI information from the phones on Swappa. Additionally, I would have to pay sales tax of $36 on the phone if I were to buy it from T-Mobile.

I believe I would save around $100 if I bought a, for all intents and purposes, a "new" phone on Swappa rather than from T-Mobile. The downside is that I would have to pretty much pay the cost of the phone all at once. Sometimes, sellers will throw in free stuff like a case and a screen protector, so those would be a nice bonus. Anyway, this would lead me to purchase the G4 from Swappa, but I was wondering if there was something I missed that T-Mobile had over Swappa?

 

Many thanks.