I tend to be a bit of a techie who ends up bringing one of each on my long bike trips (laptop, kindle fire, kindle reader, phone...) but I also recognize where each one is best and how I use it. Here are some of the pros and cons I've found:
1) Kindle paper white device. Great if my primary purpose is reading. One of the things I really like is it has built-in GSM network that I can use to download books - even sometimes way far away from towns. More than once, on trips through Africa and South America, I was in my tent not in a town but able to download the next book to read. I also like the "email to" feature where I can send documents in advance that I might otherwise look up later. It is lightweight even compared to a book and long battery life is also nice.
The downsides are what it doesn't do. Some books like Lonely Planet guides have maps that aren't easy to view - others are ok, but definitely best with more text. It also isn't something I typically use when underway.
2) Laptop. This is the other end of the spectrum for me. I like keeping up a blog and like some of the photo processing software on the laptop. I'll bring an extra USB key and boot into linux and do some random programming at times. On my South America trip I worked on writing text for a book. Some of these things I might be able to do parts of on a tablet, though I like having a separate keyboard/screen as well as some of the software.
3) Phone. This tends to be more of my "while underway" device. The GPS is useful, even with offline maps like MAPS.ME. At times when I've traveled with my brother we've used text messages for quick syncs since we don't always bicycle in lockstep. I almost never use it for calling since I don't necessarily know people in the countries I visit and don't get into habit of calling back to the US. I did use it once or twice for this purpose, e.g. in Bolivia when one of my investment accounts was sending messages about not my ground mail bouncing back in the US - so I found a local access number to dial into their network. However, it is rare to use it as a phone phone.
4) Kindle Fire tablet. Not sure I really need this as functions overlap #1/#2/#3 above - though I've had it along anyways. This would be a reasonable platform for viewing videos - at least if you have the wifi bandwidth where you are at. It is also at least as good as he Kindle Paperwhite in viewing books and like the phone can do a good job of podcasts. It is better for typing on than the phone and less than the laptop.
I don't really need to bring one of each - so on a six month trip if I needed to cut down it would depend a bit where I was going - and then here is how I would prioritize it for me:
* In a lot of the world, I've found internet cafes to be less prevalent than 20 years ago, particularly outside the touristy areas. There are more phone networks and more people have internet at home. There is also more wifi. As a result I still like that laptop as a fairly powerful and versatile platform for whatever comes up. So I'd probably still bias towards bringing that with me. However, if I didn't then I would bring a tablet instead.
* A phone is fairly expendable for me - particularly if I'm not planning on sending text messages. So that is more optional than some other pieces.
* The Kindle Paperwhite and Kindle Fire overlap functionality at least if I also have a laptop - so depending on whether I brought a laptop I might bias towards the Paperwhite.
So if I were cutting down and only bringing three items, it would likely be: (laptop + paperwhite + phone) or it would be (laptop + paperwhite + fire)
If I were only bringing two items it would likely be: (laptop + paperwhite) or (laptop + phone)
If I wasn't bringing a laptop, it would be: (fire+phone) or (fire +paperwhite)
If it had to be just one item, it would be either my fire or my laptop.