DVD-R is the most common and cheapest format and as most drives only do -R it is usually the most common option. The Sony drive is expensive but it is a very nice drive and has been reviewed and recomended in PCA. I think TEAC and Pioneer now also do a dual format drive but I am not sure.
If you are 'producing' DVD's for other people then I would recommend a dual format drive as some stand alone players will either only do +R or -R.
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