Originally Posted by
freecia
I lean towards Android when choosing a travel specific phone/tablet if I will be picking up sims as I go. Apple iPad Air 2 has excellent LTE band support but relies on carriers enabling tethering profiles to allow hotspot/wifi sharing. It also doesn't support sms which some mifi and Android tablets running 4.2 do and can save angst to (de)activate data packages via sms. There are also several mid-priced android phablets. Lastly, my experience is that micro sims are easier to find than nano sims. If you're careful, a nano sim in an adapter is easier to pack than a chunky sim cutter.
If you want LTE, you need
a) ATT roaming (they officially support LTE roaming in certain countries) or local sim which offers plans with LTE
b) wifi device with large set of LTE bands for RTW
http://prepaid-data-sim-card.wikia.c..._common_phones
LTE Bands used by country and carrier
https://en.wikipedia.org/wiki/List_of_LTE_networks
Tablet LTE search
http://www.gsmarena.com/search.php3?mode=tablet
If you're happy with 3G, that will lower the cost and open up a lot of options. Just get an unlocked pentaband 3G phone/phablet/tablet.
Google Fi and T-Mobile post-pay both offer good lower cost roaming data options if you can live with the reduced speeds or buying speed pass (T-Mo) which is still likely to be slower than most un-throttled local prepaid sims. Google Fi is currently supported on Nexus 6 and rumors say the new Nexus devices will be released in the coming month or so. T-Mobile is nice in that if you already have an unlocked phone with quad or penta band support, you basically just need the account & sim card. You can also put it in a dual sim phone to get phone/sms at the Tmobile number and pop in a local sim as needed for faster data (aka when it is worth picking up a local sim)
It appears most Android devices sold in the US do not include LTE bands for Europe and Asia. Often, as is the case with the Nexus and Samsung phones, there is a US SKU with specific LTE support and then a rest of the world SKU, with a different set of LTE bands.
You can't even buy the latter unless you import.
iOS have all the LTE bands for both US and Europe/Asia support.
As for tethering, I've never had problems and I've used SIMs in France, UK, Italy and Belgium.
What is tricky is that they don't always have nano SIMs at stores. But if they have a nano SIM, they often have a prepaid product targeted for tablets/iPads as opposed to phones. Often this means no voice minutes, just data.
A smartphone specific plan may have tethering limitations but typically, that means a separate APN and login/password.
In most cases, these SIMs self-configure so I never had to enter the APN. But in Belgium with BASE, I had to enter the APN and the login/password from the prepaid Wiki site and had to enter those values for the Hotspot section as well.