The 4 fluorescents don't compare to one 400 watt mh of course....400 watt mh kicks out 36,000 lumens,,,,,,the 4 fluorescents kick out 20,000 which is about the equivalent of a 250 mh........and mh is better than hps for vegging only.....,,,,,,,depending on strain and method of growing is how you determine how many plants you can grow example Sea of green(SOG) or Screen of Green(SCROG) methods are used when you don't have lots of vertical space.....My tent is 4x4x6.5 feet I am going to flower 14 plants in SOG under one 430 Super Agro and fluorescent mixed but my veg room has fluorescent lights only.The mh is the way to go if you have the money and heat is no issue but the fluorescent t5 are not far behind if compared equally in lumens(for vegging)........It really depends on you the only thing if you go fluorescent get the light real close to your plants so they don't stretch and I can't answer your question about the plants growing faster with either lights because there are many other variables that affect plant growth.......,,,,,,,Hope this answers your question