Ive got no real experience of Origin. Steam on the other hand I think is great, especially when there's a sale on...
I have no issues with the steam software itself, I find the store easy to use, I can find the bargains, I can find the games I want in the market no problems, checkout with paypal is simple enough, set the games downloading and a few hours later they are ready to play.
Ive got a lot of titles and a lot of DLC and havent ran into any major issues in the years Ive been using it. 70 titles on my own account (tons of dlc) plus many more on the accounts for my wife and the kids that have their own accounts so far.
If I had a internet connection that wasnt upto the heavy data use then it would be an issue. But the software itself I cant see that its so bad, it can get a little slow when theres a big sale on, but it works fine, at least I find it easy enough...