Key considerations for an ideal travel laptop are portability, storage space, battery life and the price. You should look beyond the more obvious specs such as the processing power. A laptop that is versatile and lightweight is every bit as important as the power of the processor. A travel laptop needs to be easy to use and offer bags of storage space. Mobile data and Wi-Fi is never guaranteed when you are travelling, so storage can be crucial.
For a basic and functional travel laptop, a Chromebook is a good choice. They are not for everybody, but for regular browsing, watching video, basic work tasks and backing up files from a cameras or other device, Chromebooks offer an affordable solution.
Devices that can be used both as a normal laptop and as a tablet give you useful versatility. There will always be times when you need a full laptop. Equally, especially when you are travelling, the option of a tablet can often be much more comfortable and convenient.
Convertibles tend to be a little less powerful than conventional ultrabooks, but the extra versatility makes up for this.
The laptop category that was really pioneered by Apple with the MacBook Air and then all the other brands followed the lead. Ultrabooks replace slow HDDs with the efficiency of SSDs and are lightweight packages. SSDs tend to be on the small side compared to HDD, so it might be that you need an external drive if you have a lot of files.
Your choice of a travel laptop that is right for you will be determined by what you intend to do while you away. Each of the above suggestions has various merits, and a couple of potential drawbacks too. You just need to decide which of the pros are most important to you, and which of the cons aren't too much of a problem for you.
One downside to ultrabooks versus regular laptops is that their SSD drives are typically smaller than HDDs. This can be solved by bringing an external USB drive.