Crank lengths question

[Marcellus]

Currenly i have 50/34 chain rings with a 172.5 crank.

Looking to change to a 54/39 and have been offerred a pair with a 175 crank.

Apart from 2.5cm what's the difference and will i notice?

[Marcellus]

Really 2.5mm??

So unlikley to notice then?

[Marcellus]

I think i'll suck it and see how i get on, i can get the new crank set for only £20 nearly new so not a massive cost if i don't get on with it.