I have three. The first was the Union Pacific TTT-6 (2-10-2), and I found it to be a stunningly fine locomotive. Thankfully, the whistle is correct. Caused me to rip up three feet of groomed track, but it had to be done to get it around a sweeping wide descending curve. The tender kept derailing. It was fine after I elevated the outer rail on that curve about half a mm.
Second one was the PRR Q2 Duplex 4-4-6-4. Another home run as far as I am concerned. BLI batting 1000. Only annoyance was with the whistle. Its sound is okay, but obviously looped, something that BLI seems to have acknowledged as a minor fault and have corrected in their latest catalog announcement.
Lastly, the new UP Union Pacific class 4-12-2. Once again, execution is excellent, at least on par with the other two. Good quality control. Everything works as advertised. The whistle...should have used the QSI sound file for the UP TTT-6 because they were the same. They thanked me when I suggested they get the rights to that file, or at least find a way to get the right whistle. They didn't. A miss. It is fairly close, but the TTT-6's whistle was spot on.
I can't say the drives are different between the Paragon 2 and the Hybrids (they seem to have abandoned the "Brass Hybrid" name and all are Paragon 2 in their latest catalog). I believe the only difference is that the shells are brass components. Most fixtures, appliances, frames, etc, are typical for BLI, metal or plastic as they can acquire them or make them cheaply.
Although it is hard to be absolutely sure, it seems to me that the brass models are somewhat heavier. They have a heft to them that the other similarly sized locomotives don't have. It could all be psychological, though.