I have this exact same issue. Heated opinion on either side - maintain the liquid temp or maintain the mash temp. Frankly, I've never seen a well supported answer either way.
I'm leaning this way - shoot for the middle. When mash temp and wort temp vary by more than a few degrees, speed up the recirc and stir to bring the temp back closer to equilibrium, then slow down the recirc and drink a beer.
Note: I don't think that anyone, without a very well insulated mash tun can have these two temps match perfectly throughout the entire mash process.