are they just as good?
Oh boy, here we go . . . down the wild, wonderful rabbit hole known as Caps!
I suspect they are. I'm a fan of the ECW series (polypropylene as the dielectric rather than polyester for the ECQ series). But don't have much data to back that statement up. The Panasonic data sheets are very good, worth a read.
715P (and maybe 716) Orange drops have been the go to for years. There is published data for 250V rated Orange Drops that suggests lower distortion than other caps (looking at you, WIMA), but I can't find other data for 630V rated caps.
In my basement lounge, also known as my "shop," I have a lot of ambient electrical noise due to LED lighting and my air handler. I do an "outside foil test" on all my caps, and when I hook up the Panasonics -- either the ECW or ECQ series -- to the 'scope, there is normally less noise present on either end as compared to the 715/6 ODs. I don't know what that means, to be honest.
The Panasonics are much smaller, much less expensive, and I haven't seen any noticeable difference in tone. As an example, I've been experimenting with Dumble style amps for the past couple of years, and have built some with 715P, some with Panasonic ECW, with no notable difference. In fairness, due to the complexity of the Dumble switching, noise issues are all about proper lead dress.
Anyway, the Panasonic ECW and ECQ caps are much smaller, much less expensive and seem to work great.
As an aside, I think the Orange Drops are so much more expensive because they are obsolete in modern devices -- they're just too big! But, they are great caps.