I don't know much about LEC or CMH. I would personally use either HPS or LED for flowering. But in this case, I woul definitely go led. Size of tent matters, in a 2x4 tent I would go with a long skinny led like one of the following. Much better coverage than using hid with it's single point light origin.
Ultra High Efficiency LED Boards for DIY. QB288 has 288pcs Samsung LM301H LED. 260 Watt Lamp Kit suited for main light and supplement lighting.
horticulturelightinggroup.com
Ultra High Efficiency LED Boards for DIY. QB288 has 288pcs Samsung LM301H LED. 320 Watt Lamp Kit suited for main light and supplement lighting. 3 ft. long heatsink for a wider spread.
horticulturelightinggroup.com
I have the 260W version I bought for a 2x4 tent I have. Used it once and it worked very well. If I were to do it over again though I would go with the 320 myself, but either one is fine for a 2x4.