Between the two burners, the Pioneer is definitely the better one. The burn quality is quite a bit better than LGs. Having got both drives, and having burned different brands of discs with both, I found that the quality scans of the burns done with the Pioneer were consistently better, sometimes by quite some margin. Based on what I've seen on the forum, I was expecting the LG to be quite a good drive, but it turned out to be quite a disappointment. As such I would highly recommend to get the Pioneer. It is more expensive but IMHO its worth it. Blu-ray media is expensive and having a reliable burner is a good idea (getting Blu-ray coasters is rather frustrating and expensive).
PS. Although in this case it turns out to be true, quite often a higher price tag doesn't necessarily mean higher quality. At this stage, Pioneer BD-RW drives are the best the money can buy.