Would I be getting more useable light from two 1500 lumen CFL's or direct sun through a windowsill?

I've got a south facing window that gets pretty direct sunlight most of the day and then when it gets low I've been putting my seedling under the CFL's at night then back in the windowsill during the day. I've got a 600w HPS/MH that I'll have set up in a few days and these are still small seedlings with only the cotyledon and first leafset coming in, about 6 days old. Should I just keep it under the CFL's all the time until I get my HID setup or is rotating them into the sunshine in my window like I've been doing gonna get them more juice? I want to keep them from stretching as much as possible until I get my tent ready

Direct Sunlight is going to beat out CFL's anyday of the week.

JavaCo said:

Direct Sunlight is going to beat out CFL's anyday of the week.

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I wasnt sure how much diffusion happens between the sunlight passing through the screen and windowpane