ESET vs Emsisoft is an interesting dilemma because they're literally the best at the opposite things.
Emsisoft has one of the best behavior blockers on the market for preventing malicious zero-day software from performing harmful actions on your machine. ESET on the other hand has a difficult to configure HIPS which can be very powerful for configuring custom system-wide rules but in its default configuration provides almost no harmful behavior blocking of zero day threats. It happily allows home-brewed malware to register startup items, phone home and download another executable payload, encrypt everything in My Documents, etc etc etc.
On the signature side, the opposite is more or less the case. ESET's signatures are class leading, and if 3 detections exist on VirusTotal, ESET is almost always one of those 3
. Meanwhile, BitDefender has been letting their signature-based engine fall behind significantly. It takes them a while to add to their signatures database, and it seems like all of their R&D is on the "Theta" AI engine (which is not yet available to shipping products). It's still not awful but it's measurably behind the pack leaders.
I view the two as differing philosophies: Emsisoft's behavior blocker is pretty much its savior and what keeps it overall performing like a top dog despite the signatures sometimes catching less than half of the samples in a malware pack on the Hub. But I do not recall the last time Emsisoft allowed any malware to encrypt documents, for example. The worst "infections" I've seen appear to be hollowed out processes sitting dormant and not doing anything actively malicious other than maybe the occasional AutoRun. OTOH ESET's more or less the posterchild of the "if your signatures don't suck, you don't need a FP-prone behavior blocker" philosophy. Just a week or two ago, ESET allowed a piece of undetected malware to encrypt user documents. Basically if it slips past the signature engine you are more or less toast.
In the end I think it depends on what you do and what kind of protection you're looking for. If you're the average PC user, I'd recommend ESET. Good signatures catch what you're likely to come across. But if you are a high prized target for custom-written malware, or deal with a lab of students who know how to write malicious programs, or frequently download freshly pirated software before signature DBs could catch up, I would lean towards a strong BB product like Emsisoft.
(In my opinion there are other options like F-Secure, Kaspersky, and even Norton that strike a better balance of walking and chewing gum at the same time.)
