Although they have many of the same goals in mind - increased privacy, anonymity, encryption of web traffic, etc. - VPNs and Tor are not the same thing. They have some subtle and some quite important differences, and achieve their goals through quite different methods. This article is a good place to start to learn the differences: https://thebestvpn.com/tor-vs-vpn/

No one can answer what the "best choice" is for you, because it depends on a lot of factors such as your geographic location, what your online activities are, what you are looking to achieve by using one or the other, things like that. However, if you have no budget, then using Tor (which is free) is far superior to using nothing or using a free VPN. (Using a free VPN may actually be inferior to using nothing, as they are almost certainly collecting and selling your data to make a profit).