You decide: Fast internet or lots of offline storage. Or medium internet and lots of offline storage. Gamer might want fast internet for low latency anyway as well as large downloads once or twice a month.
if you can download your games in a reasonable time frame then you don't need much offline storage. Probably 4 or 5 large games installed at once is more than you could play all day or all week for that matter and I should think that 1tb + fast internet is very manageable.
Offline storage makes it convenient to reinstall like a jukebox more immediately but you could also opt to only offline store large games.
And you might also want to back up your offline storage so network attached storage so once you're done thinking about it have quadruple redundancy: The online store you can redownload from , the game installed on your disk, the offline storage and the offline storage backup.
It depends if you just want fast internet anyway. Slower downloads once a week or twice a month or something with plenty of storage is probably cheaper since drives are probably cheaper than your internet connection if you only spend 100 or 200 a year and they last 3-5 years under warranty it's way cheaper than 20 a month internet /240 a year or should I say 200 for 5 years or even 400 for five years of more backup sol'n is cheaper than 2000 for 5 years of fast internet. So a slow or bearable medium connection plus offline storage is more probably somewhere in the range of an optimal price/performance ratio.
where a fast internet connection only is way more expensive than a medium connection and offline storage. In a perfect world Fast internet that was cheap as dirt would be better. Then you'd only have dual redundancy: The game installed on disk plus the online store.
But since internet connections go down and drives fail you might even want a spare backup internet connection if 100% uptime was your goal.
It all depends on what you want, what you need or what you can manage with.
I'm coming from a different set of circumstances. 8 year ago internet deals were bog standard and drives more expensive. Well the internet deals are probably still bog standard and drives are cheaper but if you shared a house and only paid a fraction, the calculus could be a bit different.
I have a 256gb os drive, and 2 256gb sata 3 drives so I bought a new one mid-way through the warranty of the other, a 1tb hdd and another 320gb hdd so bought in dribs and drabs over 8 years that's 2 terabytes about 2/3rds full with about 80 games in storage of varying sizes from the days when data wasn't quite so huge plus more that I could download on demand if I fancied it and the time to renew my isp contract is rolling around so I could stand to get another 2tb storage drive or two for another backup and maybe not need so much if the internet connection speed is what's advertised.