Good brands are LiteOn, Pioneer and Sony.
And yip, at this time you should really be looking for a dual-layer burner (has a capacity of over 8G

. Pioneer makes one which is dual-format/dual-layer:
http://www.pp.co.nz/ProductsA.php?pp_id=DW00052
The - or + decision is cancelled out since the Pioneer DVR-108 burns both formats (dual-format).