Just an update after a few weeks;

I left T-Mobile and switch to Google Fi. I loved T-mobile's international coverage as it allowed me to stop switching SIMs while traveling and to do basic things (google maps & check email). One couldn't do social media however or anything that required faster access.

I finally tired of the slow access and switched. Wow. Google Fi is much better... abroad.
I received 10 Mpbs down in Taiwan and 5 Mpbs down in Thailand. I can do anything just as I do it in the States. No problem connecting (quite similar to how T-mo does it). Takes just a minute or two after landing. Of course I pay for this speed - but at $10 per GB I'm more than happy to do it. Winner for International service - Google Fi

However, in the USA I'd say T-Mobile is better. Weird that since Google Fi uses T-Mobile and/or Sprint - whichever is better depending on your locale. But in actuality it doesn't work as advertised. Here's what I mean. If I am on T-mobile via Google Fi - then Google Fi wins. Speeds are fast and exactly what I got from T-Mobile. If that was all - it'd be clear Google Fi is a winner. But sometimes where there is no T-Mobile it switches to Sprint. That works... but if/when Sprint gets one or no bars... the phone tries desperately to hang onto Sprint. Even if T-Mo now has more bars. So I have to force switch it back. Once I do that the phone is good again. It might seem like an easy thing to do - but you don't realize this is why the phone isn't working until a few minutes of frustration wondering why things are not downloading. So the seamless switching doesn't work properly. Weirdly I'd almost prefer to force keep the phone on T-mobile and I'll tell it when to switch. I used the phone in Miami, Vegas and Los Angeles. I'd say Domestically T-mobile wins... slightly.

Since I travel Internationally A LOT, Google Fi is a clear winner for me. If you are Stateside a lot - then I'd say stick with T-Mo.