The important thing to focus on is quality. You need to make sure you cover the topic as well as possible, check for grammar and spelling, reread it to see if it all makes sense. Then add the links, photos, polls, etc., to make sure that it is an interesting hub that provides value to your readers.
You will get better long term results with quality hubs.
I personally don't limit myself to one hub a day. It takes me about 2-5 hours for me to write a quality hub, and I usually work on it over several days. Sometimes I can finish more than one of these hubs in one day, since they were started earlier. When I do that, I try to leave a few hours in between postings though, so that the first one has a chance to get some reads before the next one comes along.
When I am not working, I have the time to devote 8 hours to writing hubs, I can get several out in one day.
If you can write more than one quality hub in one day, then go for it. You'll get a bigger portfolio faster that way.
But remember to keep the focus on quality. Do not sacrifice quality for quantity.