Heres some things Ive found on DVD-R/RW versus DVD+R/RW.
More compatable with set top DVD players. It is an approved DVD spec of the DVD Forum
. You are in good shape with a DVD-R/RW burner if you wish to view your burnt DVDs (IE: if they are video). The only disadvantage is that DVD-R/RW has been known to take longer to format than the DVD+R/RW spec, but higher speed DVD-R/RW media and burners has all but made this problem disappear.
Much less compatable with set top DVD players than DVD-R/RW, DVD+R/RW is mainly tailored as a gross data holding disk; though it can and is used frequently by users for video purposes. It is only said it is not a great video disk because DVD+R/RW has a higher instence of not playing on DVD set top players than DVD-R/RW. It is the approved media of the DVD Alliance
An advantage of DVD+R is that the media is a bit cheaper than DVD-R media;
on Newegg.com, I found a 3 pack of Memorex DVD-R media that cost a bit more than a 5 pack of DVD+R media (the DVD+R also have jewel cases).
So, if your laptop has a built in rewritiable drive, I bet it is a DVD-R/RW drive. (Note: Laptop DVD±R/RW drives exist and are wuite common on higher end and media oriented models.) This is good. Be happy with it because it will serve you well in the future should you desire to make DVD movies. Also, I suggest you reconsider buying from that computer store again if the sales people are giving you false information.