Acros is an extremely fine grained film, and will likely be finer grained in XTOL at various dilutions than with Ilfosol (which operates at a significantly higher pH). While generalizations are difficult, assuming a constant contrast index, 1:3 will be slightly grainier than 1:1. Pretty much nothing else will happen, regardless of whether you agitate every minute or every three minutes. Longer agitation intervals can sometimes give the impression of increased sharpness if edge effects are enhanced, but I doubt you'd observe anything significant under this scenario. With general purpose solvent developers and current films, differences in image structure characteristics due to changes in agitation and/or dilution tend to be greatly exaggerated and clouded by subjective responses. For example, an increase in graininess often leads to a perceived increase in sharpness. Even the shape of the characteristic curve is more difficult to change than people assume.
The best thing is for you to try XTOL and stock, 1:1 and perhaps 1:3, under the same controlled exposure conditions, and developed to the same contrast index. Make some prints and decide what you see.
