I can now offer conclusive proof that an SAD lamp is not as good at sunlight. Consider these Taxi tomatoes:

Sunlight versus OTT-LITE

The plant on the left was grown on my windowsill. The plant on the right was grown just below the windowsill, under my OTT-LITE lamp. (Admittedly, a couple of feet overhead. But it seemed fairly bright.) These are the same variety from the same packet of seeds, planted at the same time, treated identically until a few weeks ago when I transplanted and had too many plants for my space. Next year I’ll use fluorescent lights.