http://www.apple.com/shop/buy-mac/imac?product=MK142LL/A&step=config
id be unsung it mostly for reports and videos
http://www.staples.com/HP-Pavilion-24-b016-All-in-One-Desktop-PC-Intel-i3-Processor-8GB-RAM-Memory-1TB-Hard-Drive-/product_2257012
http://www.bestbuy.com/site/lenovo-700-22ish-21-5-touch-screen-all-in-one-intel-pentium-8gb-memory-1tb-hard-drive-black/5196200.p?skuId=5196200 Very little, performance-wise.
They are all in effect laptop-grade systems built in to monitors.
None are suitable for gaming etc., just basic desktop type stuff.
I would _never_ advise getting an all-in-one machine for general use, they are not upgradable and if anything goes wrong you have to replace the whole machine.
If you want a minimal-power machine with a bigger screen, get a mini PC or a secondhand Mac Mini and a standard monitor, whatever size suits you.
eg.
https://www.amazon.com/...B00SD9ISIQ
http://www.ebay.com/...2238393132 One runs macos. The better value, and more useful for the future one, runs Windows!