Happen to have a portico/7xx comp handy (of regardless of whether it's the akgs or otherwise, just curious about the differences)?
It's pretty easy for me to pull some samples of the various configurations if you would like to hear them but it's not going to be a controlled comparison.
IMO: The 722 sounds a little bit loose down low compared to the Grace and Neve boxes.* There is something to the 722 sound that doesn't really seem to be as crystal transparent as the V3 but I wouldn't call the 722 sound veiled. But whatever is going on with the lower end seems to balance really well against the HF bump of the 414XLS and neumann AK40/43 caps.
When the Neve is running with silk disabled, it sounds very close to the V3 across the samples I have made. Currently I'm running TLM170s when I can run open and 4023s when I need to be small. Both of those mics are more flat than the 414XLS and AKxx although the 170s are not purely flat. I think that both of those mics sound OK directly into the 722 but sound best though the V3 and Neve and the Neve especially with the silk mode on. I really love the silk mode of the Neve and run that all the time. If I had to pick a preamp for the 414XLS (of those I have experienced over a few years) I believe Neve+silk, then SD722, then V3 or Neve without silk.
* there was some discussion in another thread that the V3 may roll off some of the lower bass. IIRC SD claimed that the 722 is flat all the way down to DC. So if there is a roll off in the V3 and Neve, it could be the low end thing is from the mics. ymmv
edit to clarify XLS