Err, back on topic.
Take the exsiting shower head off and run the water. If there is plenty of flow choose whatever shower head you like. If there isn't a lot of flow choose a shower head with small holes - water saver type showerheads. And remove the flow restrictor.
In a rental of my GF's I looked at the shower and thought I could pee better than that and GF didn't want to buy a new shower head because the shower was no good anyway... So I bought a fine holes type showerhead for her and the tenants love it.
Another tenant used to have 45 minute showers and complained of running out of hot water. I put the same type of showerhead on but with the flow restrictor and she loves it. She thinks there is a bigger hot water cylinder
