If money is no object, it seems Bose is the way to go according to most pilots that have used them.
If money were a factor however, and you just wanted to get ANR for the best price, I would recommend the PilotUSA PA1779-T. It was the first headset I ever bought, used from eBay, on recommendation from my ENT doc who also flies. According to him, from strictly an ANR standpoint, they're just as good if not better than Bose, and they're what he flies with. Being a doc, money is no object for him, but he insisted there was no reason to pay $1,000 for an ANR headset. However, after using them for about a year, I can say the PilotUSA definitely not the most comfortable you'll find, and not the easiest to maintain. The ANR may be great, but the rest of the headset falls into the category of "you get what you pay for," so I'm a little in disagreement with doc on that point.
I bought a used Lightspeed Zulu, first gen, off this forum for not much more than I bought the 1779 for. I couldn't be happier with the fit and also with the ANR. Plus replacing the foam ear pads is a snap, literally. The old ones just snap off, and you can snap the replacements right in. The 1779 has adhesive-backed gel ear pads that can be replaced.
The plane I trained in had a choice of Bose or David Clark passive, both of which were fine, but I personally didn't like the way the Bose fit, so I mostly wore the David Clarks until I got my own. Not sure about all brands, but some of the newer in-ear sets appear to be marketed toward quieter environments like corporate jets and such. I have a hard time thinking they'd provide as much passive protection as an ear cup that covers the entire ear, but I've been wrong a time or two in my life, so take that for what it's worth
I agree with Henry, if you have a chance, try several different brands and see what you prefer.