Tonian Classic 12.1s vs. Vintage Tannoy MG 12

Cabinets and crossovers are important parts of the stew, and I don't know enough about your Tannoy rigging. Both will have generous midranges and full, rich tone. The Tonians may have better definition, particularly at higher frequencies, and can be a little faster (depending on the electronics). Both are easy with music, and not sharp, shouty, or grating.

No_regrets,
It appears from the photo that your Tannoys are rather close to the wall, and this placement would be less than ideal for the Tonians. You may know that the Tonian cabinets have a removable panel at the back, and the owner can use different sizes of "slat" to achieve different results, but you would likely want a little more space behind. I don't know if you have experience with ribbon tweeters, which Tony's designs use.