Long post disclaimer!
I'll throw my opinion in since I also own a 2012 F150 w/ecoboost. I'll start off by saying that it was down to the tundra and the F150 when the time came to buy. The things that swayed me was the fact that I could get a crew cab with a 6.5' bed in the f150, the 36 gallon fuel tank in the f150, and the higher payload rating in the f150 ( mine has 1700# payload, yellow sticker in door jam). That being said, my '08 4Runner has been flawless so the reliability factor was going for the Tundra. Honestly, I don't really like the interior of the Tundra. Those oversized knobs are just out of place. I've seen some videos of the 2014 tundra and I like that interior much better. Outside is other story though.
Back to reliability, there are some known issues with the f150s. If you go by the numbers on the forums, there are more issues, but there are far more f150s out there compared to the tundra. I have had two issues with mine in the 28k miles I've owned it. First was the intercooler cracked. This was fixed by ford. Second, the truck developed a slight mis in 5th and 6th gears with light throttle. Ford couldn't find anything. No surprise here, I've had terrible luck with all dealers when it comes to service. A little diagnosing by myself led me to the spark plugs. Since then, no more mis.
In my area, the ecoboost is great. I live and work close to 7000' elevation. Plenty of power for towing. I'm in the high desert of the SW so humidity is of little concern to me. Why humidity? Well, it turns out that the design of the intercooler on the ecoboost f150 is prone to condensing the charge air in very humid climates. Throw in extended steady, light throttle conditions and the intercooler can collect enough water to make the engine stumble, stall, or even damage the engine. There has been quite a stink about this all over the web. The strange thing is that not all f150s do this. It still is a small percentage of owners affected.
Some 2011 f150s were plagued by faulty transmission pumps that leaked. That was supposedly fixed for 2012 and later. The transmissions actually seem pretty good on the f150. There are a number of folks driving 500hp (crank hp) ecoboosts with no trans issues. The AC in the f150 does suck. I've helped mine by insulating the AC lines but still it should be better. My previous 150k silverado and my 4runner will throw ice cubes at you after 10 minutes.
The ecoboost does get better mpg than a tundra but not by much. Actually, mpg is all over the place for the eco. Personally, I've been getting 22 mpg with mixed driving. Early on the truck was only getting 15. It took about 22k miles for it to finally start getting good mpg. City mpg is not very good for the eco because it is in boost a lot with city driving. If your into more power, some company's are making some impressive gains with only a hand-held tuner. Like 90hp and 100+lb ft of torque gains with no impact on mpg.
In the end, it boils down to luck, or whatever you want to call it. Look on the tundra forums. Lots of leaking water pumps and blown steering racks. Little things, the OEM stereo is better in the tundra. The SYNC system in the ford is a joke. My f150 has almost as much frame flex as the tundra but it's still less than my '69 f100, my ex's 91 f150, my dad's 94 f150, and my company 97 f150. Guess thats a ford thing. Never noticed it on my gm's.
Sorry for the long post.
