big hdd's (not really big, though.. as big would mean 1TB+) are as cheap as smaller ones. and SSD's are always more expensive - and the older small and "cheap" SSD's are not as reliable as a small 2.5" HDD for example.
Sure. I think what I am really wondering is if there is any technical reason to have lots of storage on a mining-only rig.
No. The size doesn't matter only the cost.
For miners get low end CPUs with stock coolers, cheap disks, and any more than 1 gig of ram is a waste. PSUs and GPUs are the right places to spend money.