It's admittedly a guess, but it's my best guess.
I think the problem you're running into here is that an incandescent flood light would inherantly work better than a CFL flood light simply because the incandescent floodlight's filament is much closer to a "point source" than that of a CFL tube. And, for exactly the same reason, a Xenon bulb would work better in a spot light or a flood light than an incandescent bulb simply because the source of the light is much smaller in a Xenon bulb than an incandescent bulb. The smaller the source of light, the more you can count on a parabolic reflector to convert that point source of light into a spot light, and the better spot light you have, the better flood light you can design.
If you look at a spot light, you'll notice that it uses a parabolic reflector. The point source of the light is located right at the focal point of that parabola so that the light comes out of the spot light in almost a straight line. (Think "flashlight")
Flood lights work in a similar way, but they have a light diffusing cover that spreads that straight beam of light outwards so that you illuminate a much larger area. You can also get much the same effect by moving the source of light so it's not right at the focal point of the parabola, or changing the shape of the parabola so that it no longer creates a straight spotlight, but a spread out flood light.
Deck Floodlight Technology - Hella marine
(Notice that in the above link, only the first diagram shows the reflector as being a true parabola. The "free form" shape of the reflector they're talking about means that it's not a true parabola as evidenced by the fact that light doesn't bounce off the reflector to form a true "spot light" but bounces off the reflector at an angle so that it's really the non-parabolic shape of the reflector that results in the floodlight, not the diffuser cover.)
The problem is that a CFL doesn't have a filiment like an incandescent bulb, and so the source of the light isn't a point source, and so that makes it impossible to design a reasonably sized parabolic reflector that will create a spotlight for the diffuser to work with. About the only way you can use a CFL with a parabolic reflector to create a spotlight would be to have a reflector the size of a radio telescope. Then you could get a CFL to produce a very weak, very large "spot light".
A parabolic reflector around a CFL won't work properly and will scatter light all over the place, and so the diffuser on the front of the floodlight won't work properly either and will scatter the light even more. The result is that you'll get your 750 lumens out of the sucker, but it'll be going in every direction, not into the area you want to illuminate. So, the CFL floodlight will seem much dimmer when you're in the area you want illuminated and much brighter when you're outside the area that's supposed to be illuminated.
My guess is that the CFL floodlight you're buying has a reflector on it that's intended for an incandescent bulb, but the company is just putting a CFL bulb into it cuz that's what people are asking for. It might not work worth a crap, but if they sell and don't come back, then the company doesn't care. Most people buying the darn thing don't know what to expect from it, so if it's a piece of crap, they're unaware of it cuz they don't know how well it should work.
You might want to switch to a floodlight that uses a Xenon bulb instead. You'll have a much smaller "point source" of light that a parabola can work with, and the light output from a Xenon bulb is much higher per watt than that of an incandescent bulb.
That is, I think that the idea of using a CFL as the source of light for either a spot light or flood light is inherantly flawed cuz the thing is just too big to be a "point source", and without a point source you can't use a parabolic reflector to create a spot light, and without that straight spot light, you can't design a diffuser to spread that spot light out to make a decent flood light.