That is a very tough question as I will sacrifice a lot of extra features for a very good burn and I am extremely picky about PIE/PIF totals in my scoring system.
I would have to say it is a toss up between the NEC 3500 and the 3520. At first I thought the 3500 was a better burner but I have now found some media that is better on the 3520, Ridata G05 and MCC 02RG20 are two.
Ripping on the NECs stinks except for SL burns where they are the fastest and I am able to get both + media bitsetting with hacked firmware as well as RPC1. One of the most valuable features is the massive amount of firmware available.
The only flaw is scanning and although the 3520 is supposed to work with CDSpeed, I don't use it.
The Pioneer 109 has turned out to be just a so-so burner but a great ripper with the A09 hack. A major problem is a lack of bitsetting and a lack of firmware options.
The BenQ is currently dead and even though it has everything in one drive, the ripping was sporadic and slowed down all the time so it was not really a fast ripper with the speed hack. It really does not like -R media almost as much as the older Liteon drives. In general, I could burn any of my media on another drive and get better burns than the BenQ. With the increase in drive failures I would never recommend it.
The LG works with RAM, which I need. It also have turned out the best burn I have ever made. It offers bitsetting with +R but not +RW so it has half the problem solved there. No scanning and very slow ripping. Also no hacked firmware support that I have found.
I don't have a Liteon 1693 as yet but it could solve the "all in one" dilemma if it can match the NEC burn quality. It already has bitsetting, scanning, and ripping down. Liteons tend to prefer +R so that could be a problem.
I would have to go with the NEC 3520 if I were only to get one drive; it is superb with both -R and +R, has bitsetting and scanning (not really needed with NEC and good discs) and a ton of firmware support. When the 4550 comes out they will add RAM as well. The only thing missing is rip speed.