The benq is good. As far as the nec, I would see if you can find a 3500 or wait and see if the 3540 turns out to be any good. I'm not saying the 3520 is a piece of junk or anything but I have heard more than once that thier have been some issues. As far as which is beter between the 3500 and the benq, they are both good drives and have thier own advantages and disadvantages. Neither is really beter, they just have diffrent strong and weak points. You might want to do some reading on the forums for each drive and see which seems like it would be sutable for you. Either way you are getting a good drive. That probably didn't help much but you are going to find some that say nec is beter and some that say benq is beter.
As far as +/-, again, both work well. Some drives prefer one or the other in which case use what your drive likes. Most stand alone players these days will play +/- just fine. The most compatible is a bitset+r (bitsetting basically makes the disk identify itself as a dvd-rom rather than a dvd+r). You must have a drive that can bitset. -r is a little less compatible and a non bitset +r is a little less compatible than that. All are pretty compatible with most players (the newer the player, the beter the chance). It gets a litle more complex than that but in the long run you will want to find certain medias that work well with your burner and play on your players. You cannot make a disk that is guarenteed to play on all players but with good quality media that you know is burning well with your burner, you can get disks that are liklly to play on most.
Learn to think of dvd media in terms of media codes, not brands. Many brands may use several diffrent medias from several diffrent manufactures. I would worry about getting a drive first and then worry about media. You want to look for specific media, not a certain brand. You did hapen to mention two good medias though. Maxell 8x+/- are actually made by maxell and are good quality. Verbatium 8x, 16x+/- are all mcc and are all good quality (though some prefer ones made in certain countrys because a few diffrent companies make them even though they all carry the mcc media code). To give you an example of it not being that way, maxell 4x+r are usally ricohjpnr01 made by ricoh, not maxell. Ricoh hapens to be good media but that is not always the case. Memorex may be any of more than a dozen diffrent manufactures and in the past I have generally recomended against it as it ranges from very good to total crap. Memorex has recentlly been using moser baer which is gaining a good reputation recentlly and the memorex that is moser baer is easy to identify (MB is the only media made in india).
You can download a free program that can read the media codes off disks so you know exactly what you have purchased. Further, thier are many discussions about what media is what here, and after you get a drive, we can make some recomendations to get you started.
Fyi my choice would be an nec 3500 because it can burn just about any media you throw at it (it has beter media compatibility than most drives). Then again, the benq has beter testing capabilities which doesn't mater to me as I have a liteon burner for testing but it might mater to you because you don't have a liteon for testing. Like I said, thier are tradeoffs but they are both good brands.
Sorry if that confused you more, just trying to put it in perspective. Perhaps some benq and some nec supporters might like to give a few more strong points of each drive (or like I said, read the nec an benq forums as thier is lots of info thier).
This is the program that will read the media codes off disks. As far as I am concerned it is one of the first and most important things you will need after you get a drive.
Hope that helps some.