Both will typically result in decent to good germination, but the cultipacker has the weight and design to do things the drag harrow cannot. Most notably, on plots with any slope at all, a cultipacker will quite literally "pack" the soil, while also creating distinct rows that cause water to collect and soak in, rather than run off. You reduce the risk of soil erosion while also helping with moisture retention, both of which result in much better germination and plant growth, on sloped ground. A cultipacker is also much more effective at smoothing out ground that has been disced or tilled, compressing it to remove larger pockets of air, leaving a much better seed bed.
If you are using a no-till, throw-n-mow approach, on level ground, the drag harrow might be just as good as a cultipacker.