I've used TurboTax almost every year for the last decade, except one in which I used TaxACT because it was a lot cheaper (my taxes are moderately complex enough to send me into the more expensive TurboTax price brackets).
At the time the software felt shoddy compared to TurboTax in almost every way; it was certainly better than form-filling myself but it didn't inspire confidence.
I'm an independent consultant, use QuickBooks throughout each year, and have used TurboTax for quite a while out of inertia from having my data already in a friendly format in QB. I finally decided to give an actual CPA a try last year. Among other things, she has already saved me an order of magnitude more than her fee just by amending my old TurboTax returns. Not to mention the value of the time that she has saved me.
I would never go back to TurboTax (or TaxACT or similar) unless I was a straight W-2 salaried employee (and only maybe then).
http://sunlightfoundation.com/blog/2013/04/15/tax-preparers-...
Unfortunately, even TaxACT is a member of a lobbying group which fights against making filing taxes easier (ACTR).
I find it hard to believe there are tons of them out there unless perhaps tax software is regional software and there's companies in some states that don't move beyond the state?
Disclosure - I'm the CEO of Common Form[2]. My co-founders and I are all ex-Intuit employees. We currently only cover the 1040EZ, but we're expanding as fast as we can.
[0] http://apps.irs.gov/app/freeFile/jsp/index.jsp?ck
edit: formatting.
I just did TT and it cost me $37 for what TaxACT wants $12. Further if you want to pay from your refund, there is hefty $37 extra with TT. It looks like TaxACT doesn't have this fee...
Most likely the result of your return should be the same from both companies, as long as they understand tax law, and I would assume they do otherwise they would be gone long time ago.