The answer is "it depends" - you can't just blanket say that one is better than the others. They each have strengths and weaknesses. Tradestation is great as long as you need to only test single securities. If you need to test a portfolio, then Tradingblox, Tradersstudio, Wealth-lab and Amibroker are all good choices.
Up and comers include Right Edge Systems and a host of other ones...you have to try them out to see which one works for you.