...Ring I'm used to, just with different singers.
Karajan once said, re the chamber music comment, that his secret was that he could make the massive string forces play with such precision that they could achieve real pianissimo. There was more to it than that, though. His emphasis was always on sheer beauty of sound; he uses more fluency than Solti, and is less explosive on dramatic moments -- only slightly, but it has a cumulative effect. He tended to cast lighter voices, and make heavier ones, like Jon Vickers for example, stress the lyricism, even to the point of crooning -- compare Vickers' Siegmund for Leinsdorf. In those circumstances, in the theatre, I believe Karajan tended to keep the volume down somewhat; on recording that could be adjusted, although not always successfully, as with the somewhat inaudible Jess Thomas in Siegfried. Likewise, compare Karl Ridderbuch's Fafner, who really is the "beautiful dragon" that Kurt Bohme wanted to be, and his smooth Hagen alongside Gottlob Frick's snarling tones.
That, I think, is the origin of the chamber-music comment. It had also been levelled at Rudolf Kempe before him, in contrast to the huge and weighty approach of Knappertsbusch, Furtwangler and the like, with whom Karajan's priorities also differed. What did cement the chamber-music verdict, and I think deservedly so, wasn't the Ring at all, but the appearance a few years later of his Dresden Meistersinger.
As regards Solti, one has to remember that in those days, for most people, there was only the Solti Ring. Even individual operas, like Furtwangler's and Leinsdorf's Walkure, were hard to find or withdrawn. When Karajan came along the contrast, especially with his singers -- casting Fischer-Dieskau as Wotan, for example -- seemed enormous. Also, Solti was very unpopular in some quarters, evoking mutterings of vulgarity and sometimes anti-semitism -- his car was vandalised at Covent Garden, among much else. One minor British composer/critic, who despised Karajan, hailed the arrival of the DG Ring simply because it wasn't Solti, and that not uncommon attitude tended to play up the differences between them -- no nasty sound effects, for example. But now we have so many different performances that the similarities are, I agree, much more apparent than the contrasts.