When traveling internationally, you might want to consider renting a wifi egg aka mobile hotspot device, especially if you don't know the language, aren't familiar with the area, are addicted to social media, or traveling alone.
Of course you can find wifi pretty easily these days at establishments like cafes, stores/malls, and museums, but it's more of a convenient factor to have wifi on hand should you need it. I wouldn't consider it something essential to your trip, especially if you'll be visiting areas that are quite technologically developed.
When I went to Korea last year, I used Pocket Wifi Korea. It was convenient, decently cheap (especially if you're sharing with a friend), and I'd for sure rent one again the next I go. I'm actually renting one when I go to Europe next month so I'll probably update this post once I come back with my thoughts on how it worked in Europe vs Asia.
In Korea specifically, I noticed a lot of AirBnBs let you rent one for free, which is a crazy great perk, but obviously only for the duration of your stay. So if you're staying at multiple AirBnBs/hotels, you'll only be able to use it during your reservation.
uses for wifi egg
Most devices should...
The only CON I can think of is that it heats up easily!
How to choose
Companies vary in product and plan. To find the right one for you, consider these questions:
wifi egg vs. sim card
I used a SIM card during my trip in Australia for the first time. I used my friend's old Australian phone, went to a local grocery store to buy a reloadable card, activated it online, and then started using it. I bought 10 GB worth of data for $30 (it was either that or $10 for 2 GB or something similar). 2 GB still would've been enough for me since I was there for only 4 days, but the offer enticed me.
I also had my phone and didn't want to use her phone to log into all of my stuff so I used her phone mainly as a hotspot to have data on my phone.
The phone I used was an iPhone 4 so the battery died quickly, and it got so so hot. Even after I connected hotspot to my phone, if it was idle for like 15 minutes, I'd have to reconnect it again if I wanted to use it.
Now that I think about it, I think the policy nowadays is that your network provider will unlock your phone for you but it's something you'd have to go into to do, and not sure if there's an additional service charge for that.
My advice: if your phone is compatible with international SIM cards and you don't mind the trouble of going into your provider's store, and buying a SIM card when you get there, then by all means, go for it. It ended up being about the same price in my experience. I think after experiencing both, I prefer renting a wifi egg at the airport, making it simple and easy!
Below is a post that might be helpful if you're considering which to get.