On Beethoven:
I am now up to 18 complete sets, and I will cheerfully admit that this is pathological. Two outstanding sets that I don't think have turned up in this thread are Vanska/Minnesota/BIS and Dausgaard/Swedish Chamber Orchestra/SIMAX. Both conductors show strong period-practice influences--fleet tempos, antiphonally divided violin sections and low strings on the left--with solid orchestral playing captured in fine sound. Dausgaard is a bit more adventurous, but his recordings are on seven individual discs that are expensive to order new and hard to find in the US. I was patient and waited for reasonably priced copies to turn up on Amazon Marketplace. Vanska occasionally sells for $30 at ArkivMusic, an irresistible bargain.
I agree that the Blomstedt set is superb, and it's sad that so few of his other recordings are currently available. As is common with central European orchestras, the Dresdeners play with a sense of unanimity that is really satisfying.
I like Zinman's Zurich cycle a lot, though I wish he had divided his violin sections (as he did in the Mahler cycle). I'm not sure I'd pick any of his performances as a particular favorite, but they are bright, lively and fresh. The first movement of his Ninth struck me as absurdly rushed at first, but I got used to it and came to enjoy it.
Gardiner strikes me as undercharacterized, even allowing for the scrawny period-size orchestra. Toward the other end of the spectrum, the Czech Phil sounds magnificent for Paul Kletzki, though frequent and gratuitous tempo changes in the Eroica are bothersome. Eventually I'll slim down my Beethoven sets, but you couldn't pry that one from my cold, dead fingers. Nor could you relieve me of Jochum/Concertgebouw, music making on the highest level.
On Bertini:
I have the box set and agree that it represents a compelling and consistent view of the works, all in all very satisfying performances. But in my recent M9 obsession, I was troubled by the opacity of the recording. In particular, the first movement's elaborate counterpoint in the strings seemed to turn into mush, a pity in a passionate and intense reading.