Nowadays, the few porro's still in production with a high quality product in mind are the lowest priced entrance tickets to very high quality instruments and offer a wonderful viewing experience, especially so if you don't have to wear glasses. For the money payed, you get the best optical performance om axis. But for the aperture, they tend to be (much) more clumsy than their roof counterparts.
The views in the best of both designs are wonderful, yet significantly different due to the differences in characteristics of their prism designs and optical designs dated from very different timeframes often decades apart.
For sharp to the edge wide fields and best adjustability of eye guards, the best current generation roofs dominate the game.
For the best stereo impression at close-medium range, the porro's lead the field due to their inherent wider spaced objective lenses.
On axis contrast, light transmission and pinpointiness of stars are hard to beat in premium porro's. Only the very best roofs come close, but only at 2-3x the prices of the best porro's.
Swarovski is very open and realistic about this, having both types still in production. The startling clarity of their Habicht porro's is unmatched by even their EL or best SLC's. And it easily shows under the stars or at dusk/dawn observing nature.
We have to realize that the very small market remaining for quality porro's can have their extinction as a side effect. So if you like what these do best, get one new while you still can. Because some day, their availability new will have become a part of history. Perhaps sooner rather than later.
To a lesser extent, there is a roof prism design that I consider a threatened species: the Abbe König. With Zeiss now seizing production in there 42mm models, they only make the 54mm HT's with these prisms. And Swarovski only produce there 56 SLC's in this design.
There might come a day when binoculars with porro's and Abbe König prisms are no longer made new. Because the market put more emphasis on compact than light transmission or the highest contrast. Especially decades after use, because only porro and Abbe König prisms use total internal reflection and therefore don't need silvered optical surfaces to reflect light. And as we all know, even the best mirror coatings slowly degrade over time.
Thankfully, we can all choose an instrument that suits our personal needs best. And there is more to binocular performance than the quality of their prisms alone.