Welcome to the forum. I own both LG and NEC and it is a tough choice. Based on support from Liggy & Dee I would have to get the 4550 (I have no use for Labelflash). However the LGs do very well with stock firmware.

The main thing you are missing is quality scanning so you need to decide if you want that. Also, to help narrow the field, you should see what media is available and choose which you will be using. I assume you are not USA (no NEC 4550/51 here) and media choices can make a big difference. If you can get TY +R 8X virtually any burner will do a great job.