He's got 25mm tires now - and wants something wider. 28mm is wider than 25mm. 32mm likely won't work due to his having caliper-brakes. Why should he try 25mm when he HAS 25mm??
Actually a good 28C is as nimble and responsive as a 25C being ridden in rougher-than-road conditions. But it absorbs more of the shock going on. They are very comfortable sized tires. I run them on my utterly customized <former> Trek 7.5 FX on my personally handbuilt 3X wheels. That bike came with 32C tires. Bombproof and all around decent tires that they (the 32C's) were, I find the 28C has the best of both worlds of being between a 32C, and the outright speed-demon of my Conti Grand Prix 4000 S tires in 23C that live on my vintage Reynold's 531 racer: Quick, sure-footed, nimble, and comfortable.
I think the OP will be duly taken by 28's and enjoy them greatly. I sure was, back in 1982 when I first used them in the then-newish* 700C wheels.
* in the general marketplace - though 700C had been a standard in Europa for much longer.