Nexus 5: From Verizon to T-Mobile help (post ETF announcement)

I will make this short and sweet:

Just purchased a Nexus 5 from Google Play. It will be delivered tomorrow. My ETF to cancel my Verizon contract right now is $240. I have a perfect condition iPhone 5.

Original plan: Sell iPhone 5 on eBay (averaging ~$375 after eBay fees), use to help pay for ETF ($240) and Nexus 5 ($390 w/ tax). Sign up for AT&T GoPhone. Total Cost to me: $255

Now I'm thinking:

Take my Nexus 5 to T-Mobile and see if they will pay for my ETF. If this is the case, how long would I have to be signed up for a T-Mobile plan? From what I've read, AT&T coverage in general is better than T-Mobile (At least in Northern Ohio).

I could also just trade-in my iPhone to T-Mobile (presumably worth $200), and buy the Nexus 5 through T-Mobile for $450. Total cost to me: $250

My brain hurts. I think the most important question is whether or not T-Mobile will pay my ETF when I switch from Verizon to T-Mobile.