Not sure about this it's a road bike (equilibrium 30)
What are you not sure about? The rim is an XC rim, specifically chosen so wider tyres can be fitted. Why would you want to run a 25? Better rolling resistance? No; worse (at the same pressure). Less comfortable (yes). Better aero? Not really/marginal (25 v 28) and you're not going to be time trialling with this bike. Lighter weight? Maybe 10-20g. It's a steel frame so lightness is presumably not your key criterion.
"Equilibrium 30, priced at £1699, and one of three bikes offered by Genesis for the first time with Campagnolo components: in this instance, the alloy version of the Vicenza firm’s Athena chainset, mechs, and shifters, themselves a model year 2015 iteration with claims for reduced lever throw and improved ergonomics.
"The alloy chainset is equipped with a compact 50-34 ratio, and paired with a 12-27 cassette in further nod to the Equilibrium’s multitude of possible applications (winter trainer, summer tourer, sportive companion etc).
"The Equilibrium 30 rolls on an aluminium clincher rim from Alex, the CX26, one of many specified by Genesis this year to boast a 17mm internal diameter,
intended to provide better seating for wider tyres, in this case 28c Continental Grand Sport treads."