Anyone wanna talk me out of removing my 600MH and replacing with t5?

I have a 3x3 veg closet. Top shelf has a 8 short t5s for clones up to 18". The bottom has a air cooled 600wMH. To save heat, gain an extra foot for veg plants, and save the noise and output of another fan inside and out, I think I wanna pull the 600w in favor of a few t5s. Anyone wanna tell me why this is a bad idea? I have to buy another 600 anyway, so I could buy the t5s anduse this light elsewhere. This isn't a money thing, just practicality.

Btw, I like to veg to 2.5-3 ft

you're never going to get any where near the same results using a t5 to flower with as you will with an hps, escpecially a 600 watter.. i love my t5s for veg too, but i switch from my t5 to my 400 watter when they get to about 18 or so inches as well, like what you do it sounds.. although t5s do great for early veg as you have discovered, they don't do so well once the plants get a lil bigger as the light from them fades fast, and it's hard to get the light to the lower regions of the plants, and there fore your yields will surely suffer, a lot..