if I change from 32 x 28 to 38 x 34 will there be:

no noticeable difference?
slightly higher gearing?
slightly lower gearing?

In gear inches you’ll go .6 of an inch further per revolution of the cranks with 32-28 (I doubt you’d notice the difference)

Here

woohoo!! so pushing an (ever so slightly) easier gear 🙂

sorry for the slightly dim question but I find the numbers on this stuff completely unfathomable

You divide the teeth on the chainring by the teeth on the cassette and compare the numbers. In this case a 2% difference. 10% is a normal step from one cog to another on your cassette.

Try this Gear Calculator