They're a gift for my dad so used wouldn't be an option. I did look at the PXC 550, but those and the 4.50 both look a bit big, black, and plastic compared to the Momentum so went for them. Probably not as good, but my dad's not going to notice the difference.
The Momentum 2.0 are good. Compared to the QC35s I'd say sound quality is a bit better (possibly due to AptX HD on both my phone and the Sennheisers) but noise cancellation isn't as good (although still perfectly clear whilst flying).
They're a gift for my dad so used wouldn't be an option. I did look at the PXC 550, but those and the 4.50 both look a bit big, black, and plastic compared to the Momentum so went for them. Probably not as good, but my dad's not going to notice the difference.