Lights Panels offer an even light; it could be called soft, but soft in lighting usually refers to color temperature, not light intensity. Providing a soft light; no beams, no bright spots, no glare of light, nothing but even, soft, smooth, light.
Back-lit panels offer the best luminescent experience, with even flat light, no beams of light as bulbs provide. The initial cost of back-lit panels is slightly higher than side-lit panels, but the operating expenses are lower.
Light panels first entered the market using side lighting techniques. This is a cost effective light panel, can be thin, may have has uneven intensity, has much lower lumins per watt output, and most importantly has much higher operating costs. For certain application that require an almost surface mount look, a side-lit panel may be ideal.