The Solti with Merrill, Moffo and Kraus was my first Rigoletto too - yeah, those RCA Soria Series box sets were magnificent objects! - and I still like it. Gorgeous-voiced Moffo always sounded more sexy than innocent to me, but there's really nothing wrong with that: Krauss's timbre has never greatly appealed to me, and Merrill doesn't wring the last drop of pathos out of his part, but there's solid singing and acting all around. Solti's occasional hard-drivenness doesn't bother me as much in this opera as it sometimes does.
The Serafin with Gobbi, Callas and Di Stefano achieves a higher level of drama, but less beautiful singing. Callas is in good voice and gives us such a uniquely artful imitation of an innocent young girl that I have to love her for it even if she doesn't fool me for a minute. "Caro nome" is exquisitely felt and ends with one of the greatest trills ever recorded. Di Stefano makes an excellent, rakish Duke, and Gobbi is his expected self, dramatically imaginative and powerful, and penetrating though rather wooden of tone; I always enjoy him more when I can watch his brilliant physical acting (which fortunately we can on YouTube in excerpts from an RAI film of the opera).
About the 1930 Molajoli I have mixed feelings. Riccardo Stracciari, one of my favorite singers, here in his 55th year and generally acknowledged to have been the finest Rigoletto of his generation, is simply a paragon in the title part, vocally and dramatically. The depth and brilliance of his tone is stunning to hear, his legato is impeccable, and he alone makes this recording a library essential. Dino Borgioli is a lyric tenor of marvelous refinement; his superb legato and mezza voce create an effect if anything too delicate for the Duke, but it's certainly a pleasure to hear a tenor whose vocal ease and control would startle today's audiences. For Mercedes Capsir, unfortunately, I can't summon much enthusiasm; she isn't bad but lacks simple vocal stature, becoming a bit blatty at high pitch and volume, and she fails to project the ethereality and poignance that the end of the opera requires.