Hello,
For behaviour blocking I would say that Emsisoft would be at the top based on the amount of features they provide in their behavioural detection. However, thaat doesn't mean the other products are bad. In my opinion I would then rate GData and BitDefender both in second place. But that's my opinion.
Heuristic detection on the other hand, that's a separate story. There is no way to really tell which one is better, unless you worked at each different company to compare which one has the: better databases and better developed engine. You can try testing each product using the free trial with a lot of samples and then you could: see which one has the better detection on the samples you had and which one you prefer to use on your system. However, remember just because one product has a better detection on a pack of samples does not mean it's detection is better than the others generally speaking. For example, Emsisoft have their own engine as well as using the BitDefender engine. Therefore, Emsisoft's engine may pickup threats which BitDefender's engine do not detect. But then BitDefender's engine may pickup threats which Emsisoft's engine may not pickup. See my point?
Each product has it's own strengths anyway and other features. For example, Qihoo have a sandbox in their product. Whereas currently there is no "sandboxing" tool available in Emsisoft to have an application executed in a virtual environment. As for BitDefender, they have a Parental Controls feature, and parents may benefit from their product as well as having it all linked up to their Antivirus/Internet Security.
On the other hand, one product may have good prevention protection (good behaviour blocker), but bad signature/heuristic detection. It could also be changed round; a product may have good signature/heuristic detection, but be helpless if it misses a sample which is then executed.
Personally if you were asking this question in the case of "Which one listed should I use?" then I recommend you test out each product and see which one you like best because only the user can decide. If it was down to me, my first pick from the list would have been Emsisoft, since I know they have good zero-day protection with their behaviour blocker and they have a good and well-managed cloud network to go well and easy with the Behaviour Blocker to enhance the users protection. Of course other products like BitDefender have their own clouds too, though.
With that being said no Antivirus is full-proof and part of the BD-Family or not, there is no "best" Antivirus. User-preference only:
http://malwaretips.com/threads/why-there-is-no-best-antivirus-product.44676/
What I prefer or think is my opinion. Of course everyone has their own opinion on a product.
Cheers.
