Doing mods to the central heating...

I notice my central heating has loads of gate valves (The ones with
the red handwheels) for isolating various parts of the circuit.

However, the 'fashion' these days seems to be to use service valves
(Ball valve with a screwdriver slot).

What are the pros and cons? Why should I use one over the other? (Both
are avaivalbe locally at the same price)

Personally I tend to favour the gate valve as the hole through it
looks bigger. Any other issues to be aware of?

sponix