Why not have a play on the Windeeze game
You can try out the NATO ret and the Mildot Ret in the game and see which you prefer for holding off in the wind.
When I had a Nikko, I went for the NATO ret, even though I'm no stranger at all to the Mildot ret - switching from one to the other wasn't a problem.
It isn't really a case of carry on with what you're used to, because if you're used to a mildot ret on 10x mag, then a mildot ret on 50mag for ranging and say 25mag for shooting is going to give you vastly different dot spacings. It may end up becoming confusing for you.
As an example, if previously you were used to say giving 1 mildot of wind, would you find it confusing to now have to give 2.5 mildots of wind instead?
When I was making my decision between Mildot or NATO I looked through both on the Nikko, and I believe that the stadia lines are slightly thicker on the Mildot version. I found them to be just a bit too thick for my liking. The dots themselves seemed unnecessarily large. That could have been just my perception though, I don't know the actual line thickness figures for the mildot ret on the Nikko - they just seemed thicker to me.
As to holdover or indeed holdunder, well there are two lines below the crosshair on the NATO ret and I found them quite handy to use as my crosshairs for the really close targets (with the appropriate clicks). Although when I last used the NATO ret for FT we still had the possibility of an 8 yard target, which we don't now (minimum is 10 yards) so all you really need now are some hash marks for windage.
Holding under isn't really a problem at all. In Europe they seem to have this misplaced obsession with very steep elevated targets. I have no idea why they're so keen on those really steep shots
AlexS has much more experience of shooting that sort of course, but my opinion on it is that for the most part you can either just aim bottom of kill and/or take off between 4 and 8 clicks on the turret.
The windage lines on the NATO ret are spaced just about right. (try one out on my Windeeze game I linked to above).
At the end of the day, it won't be a complete disaster if you choose one ret over the other, you can work with either of them and the difference between the two is marginal. Whichever one you choose you'll figure out a way of using it. For me, I preferred the NATO having tried both and having previously being very used to a Mildot ret.