Assuming you are talking about an AWS VPS, there are a few things to take into account when deciding which one would be best for you. The size of your account, the number of users, the anticipated amount of traffic, and your budget will all be factors in deciding which VPS is best for you.
In general, the bigger the account, the more users you have, and the more traffic you anticipate, the more powerful of a VPS you will need. If you are on a tight budget, you may have to sacrifice some of these things in order to stay within your budget.
Here are a few VPS options that AWS offers:
-T2 Micro: This is the least expensive option, and is good for small accounts with light traffic.
-M4 General purpose: This is a good option for accounts that are a bit larger, and have more traffic.
-C4 High CPU: This is a good option for larger accounts that have a lot of traffic.
-R3 High Memory: This is a good option for very large accounts that have a lot of traffic and need a lot of memory.
You can read more about the different VPS options that AWS offers here: