Best REEL TO REEL blank tape?

I am glad this thread is alive, though I don't have any reel to reel deck. Hope to get Otari or Studer one day.
I have Nakamichi 682ZX cassette deck in top condition and use almost exclusively Maxell Metal Vertex backcoated tape. Never had any problems. This tape is the best there is for cassette decks.

I'm transferring all of my LPs to sheet music so I can get musicians to come over and play everything live. The early Jethro Tull stuff should be interesting...

I'm another R2R tape fan. 15 IPS 2 1/4 inch track tape replay is about as good as one can get, unless you get lucky finding 1/2 inch masters.

Personally I use the RMGi (now Recording the Masters) brand, which is the continuation of the classic BASF and AGFA formulations. My normal tapes are either SM911 (1.5 mil base) or LPR35 (same formulation as SM911 but on a long play 1 mil base). I use 2 x Sony APR 5003 and a Studer A807/II. I have too many R2Rs and am reluctantly letting my Revox G36 High Speed go.

The reason I put some vinyl on R2R is because some albums only have a few good songs.
Take Adam Ant,I have the entire catalog but Stripped and Vive Le Rock only have a few good cuts so I put those on tape and put the albums in a box. When the box is full I take them down and cash them in for store credit. I’m thinning out the herd,I have close to 20,000 albums and I ain’t getting any younger. It’s a process...

If you're already going through the trouble of transferring your vinyl to tape, might as well get the best sound you can. As mentioned above, 15ips 2-track on 1/4 tape is about the best you can get. The sound of tape is second to none and there's a big difference in sound quality between 2-track and 4-track. If you've already purchased the RT-909 than 2-track wouldn't be an option.