The biggest problem that you may face is not what type of DVD you should use for your own recordings but what type should you use if you intend to record something for someone else to use, (legally of course), or for use in the future on another DVD machine that you might get.
In my experience DVD-R seems to be the most compatible. That is not to say that some machines don't prefer DVD+R but I have had far fewer people saying they can't read DVD-R than saying they can't read DVD+R.
Disk brand/type and especially the batch can be critical in compatability, with even supposedly reliable disks causing grief from time to time. (I have even had recordings not playing back on the computer and drive that recorded them but then playing back fine on DVD Video players and the reverse happens with the next disk. Change to leftovers of a different batch of the same 'reliable' brand and type and all are fine - except I don't have enough of them!) Grrrr.
One final thought is durability I understand that the RW type disks won't usually last as long as the R types, so for any important or family recordings I would use an R type and put it on at least two of them. I have one regularly played DVD-R disk that is two years old and is now showing signs of disintegtation.