In my country ( Italy) prices are quite different. The R,720 are cheap but newer equipment are pricier. Also for a starter I don't think there will be much of a difference between 12th and 13th generation. Of course if the price is close the newer is better.

I think that for starters the R720 can be a good choice. It's cheap, parts are also cheap and it's a fully fledged rack server. It can have plenty of cores and ram to host lots of services to start learning.

I have some of these.

One is configured with 2x Xeon 10 cores, 192 GB ram and 5x sas SSD. Idrac is telling me that it consumes around 120W which is not that bad if correct. About the noise: obviously it's louder than a desktop but it's not that bad. I had it in my office for a few days while I was setting it up and it's like a loud gaming desktop. It's way quieter than my old Hp server or the R710.