The gear calculator shows 36/28 (1.29:1) is pretty much exactly the same as your current 32/25 (1.28:1) so stick your current setup into that gear and see if you can get up the hill!
Unless you are a strong climber 36/28 is quite a tough gear on a steep incline.
If you can fit a 11-32 cassette, 36/32 is almost the same as 32/28 with your current setup, so you might find that a better compromise.
Personally I use 50-34 and an 11-32 and on anything above around 10% I'm always in 34/32 to allow me to spin, as I climb sat down the whole way. I'm actually thinking of getting one of the new 11-34 cassettes just to get a few more rpm.
Unless racing, I'd go for the 50-34, especially if coming from a 48-32.
Thanks again Geoff.
I did my routine run today, only an hour and did all the hills in 32front-25rear......manage to get up the last tiny hill (4mins of riding), I wasn't spinning, cadence got to a low of 55.
So technically I can just stick with the bike's current setup and not spend anymore money.
Anyhow, if I do stick to Shimano, I'll still try and sell my 52/36 for a 50/34 and most likely get the new 11-30 cassette, be nice to have a rescue gear.
If I change to Campagnolo (if I get an offer for unused R8000 ultegra set) I'll go 50/34 with a 11/29 or 12/29