My personal opinion is - it depends.
If you're interested in getting good sources, for free, you really can't beat Family Search. But, keep in mind they will have limitations. A lot of good sources are available there, but it can be a trap to only use FS, as there are a lot of good sources elsewhere too.
So Ancestry, I tend to not be interested in a subscription as I'm in the US, and at most public libraries, I can get on the local internet and get their information for free. So it's a bit inconvenient to either wait for a free weekend (some holidays they will open it up a bit) or travel to the library, but I think it's worth it.
That leads to Find My Past. I believe this focuses more towards records from the UK, and if your research is taking you in this direction, you might consider this.
Personally, I try to make do with what can without a subscription and I'm able to find a pretty significant amount of information this way.