Best burner

I need to make some archival backup on DVD+R SL.

What burner is the best for the quality(not speed) of DVD+R SL?

There is no such thing as a best burner, but for the moment the optiarc 720xA or 720xS and the pioneer 116/216 or if you can find 115/215 are very good burners, notice that you will also need some good quality media, like verbatim or TY.