One computer for 3..4 years. Just a bit more frequent than console. It's all about "smat shopping" - don't buy unexpandable solutions, don't buy "cutting edge" hardware (because it's overcosted and has HUGE percentage of bad chips with new technology so manufacturers had to rise prices, etc.). And then upgrade graphics card - and 2 more years of life for your computer. (if we're taling about "console quality", it could be 1 computer per 1 console generation - their hardware is pretty similar, but PC is more flexible)
Back on topic.
Upsides:
PC: better textures resolution, bigger draw distance (in open world game it might impact your expirience), mods (including quality improvement mods one day)
Consoles: simplier to play, if you already get one - you shouldn't upgrade
Downsides:
PC: if you ask "console vs PC", I'm pretty sure you had crappy PC. And you should to upgrade it or buy (better - build) new one. You also had to learn a bit tech stuff (don't worry, you won't become a nerd ) - but hey, you must know how to drive a car to, well, drive it, right?
Consoles: worse perfomance (even comparing to 500$ modern PC), possible - 720p resolution instead of 1080p (some latest game run in 720p to reach acceptable framerates - price to pay for old hardware), tea-long loading times, not sure about community mods allowed
Generally: PC requies more from you, and gives more to you. Console is just... average, you know.