Personally I only veg with floros. There is nothing an MH can do that good CFL's cannot do during veg. The MH may be easier to work with than CFLs.

But for lvegging purposes, for me its CFL all they way.

Any light you have, CFL, MH or HPS, when used with a reflector is a heat hazzard. You can mitigate the hazzard with suction, forced fan action, kool tubes, glass, etc...

If you have a small area you are growing in, dont use reflectors.

You would be shocked to learn how many grows are killed because of heat alone.

I too, have been the clown that fried his fields with heat.

For 4 plants, definately go with the 400W over the 250W.

I am sorry but I do not know the temps of MH vs. HPS...although I can assure you that 250W of MH light is 'hotter' than 250W of HPS.

At least thats what my arms, fingers, wrists and head can testify to after all the learning I had to do