Judging from what's in the Galleries, there is no 'best' render engine. There are wonderful renders done in everything... Bryce, Poser, Vray, Vue, Cararra... it's not which one is the best, it's which one fits you best, and then putting in the time to learn how to use it. Yes, some have a lot more options than others, but if it fights your particular style or mindset, it's useless.

That being said, I did opt for Vray, because it's pretty much the standard for interiors, and that's what I do. Luckily, the interface makes total sense to me, with very few surprises. On the other hand, if I hit Render in Poser, I may as well just go grab a bottle of booze before urges to pitch the monitor through the window appear. ;)

Try all the demos you can find, and give them each a week. The ones that will serve you well will become obvious quickly (ease of import, settings logical, materials working). Then it's just a matter of reading, experimenting, and putting in the time to get comfortable with the one you chose.