When energy saving bulbs first came out I realised they did not light the room with the equivalent rating shown and I to start with could not work out why x lumen from one bulb did not work as well as the same x lumen from another bulb.
I realised there are two factors one is how intense the lighting is and two CFL or LED lamps together will not work as well as same lights with some space between them and the second was how light reflected from the light surfaces.
The 50W 2" spot light is as the name says a spot light and to light a room the distance to the item being lit can be quite large however with such a narrow spread with a normally ceiling height they need to bounce the light off a light surface.
Some just point down and some can be angled and where angled aiming them at light coloured walls can work well however they often need to be reasonably close to the sides of the room to be able to be angled to reflect the light.
Carpet is often dark and not good at reflecting light so in the centre of the room they do very little. The larger units do much better I has a 16W 2D florescent down lighter in one bedroom which is really far too bright at around 10 inches across the spread is very large but the 50W now replaced with 2W LED in the other bedroom have a very narrow beam great to read with so it will not stop some one else sleeping but with such a narrow beam does not really light the room.
So in a room with white walls and spots aimed at the walls four lamps could light the room well but pointing at a dark carpet ten may look like a planetarium lighting the room with shafts of light but leaving many dark areas.
A single 50W GU10 in bathroom everything white needs sun glasses but 4 x 50W GU10 in a dark wood shed still will not light it well even though the same area.
So where positioned and where aimed and finish of the room will affect the requirement so much there can be no real answer.
I love my GU10 reading lamp and also have some aimed at dark corners but would never try lighting a whole room with them. It's not what they are designed for.
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