Unless you are convinced that either + or will prevail then a dual format drive is the only way to go. This unit costs around £100 with a sample or each media and a decent software bundle.
Buy Now...

Installation of an internal unit is exactly the same as installing a
CD or CD-R unit. Find an empty 5.25 drive slot, with luck you will have
a spare socket on a cable if not a dual cable is supplied, a spare
power adapter lead may be a little more elusive but this unit even
comes with a power splitter an item often not supplied and all
screws you might need.
Decide if you are going to use it as a master or slave before
fitting as the jumper on the rear is a little tricky if you have large
fingers and almost impossible to switch when the drive is inserted.
This is a 4x unit meaning it will write at 4 times the basic speed,
not fast by CD standards but there are only a few 8x DVD drives out
there and they tend to be more expensive. DVD RW discs are written at
just over half this speed.
The supplied software consists of a copy of CD Creator 6.1 (the
latest as far as I know) and while it can write DVDs it can also write
CDs as can the drive. A Copy of Power DVD Software is also supplied
that gives excellent DVD movie playback on your PC.
If this is your only drive then the writing of CDs is important and
I rarely write them even in a CD writer at greater than 8x, however I
successfully wrote CDs at 16x in this DVD unit something that
surprised me as I really expected some errors. They were music CDs and
writing one in less than 5 minutes was a bonus.
However DVD writing is a more time consuming process given that up
to 4.7GB can be written in one go, the writing even at 4x is not that
quick certainly time for lunch and this is perhaps dwarfed by the
time taken to gather the information required, I would suggest that
writing all the information to an area on your hard disc is the easiest
way after all you can delete it all once safely written to the DVD.
Video files are large and this is always going to be the largest use
of DVD and these are written in the same way as data or audio files.
The CD Creator software allows you to write mixed mode discs something
that can be important.
The cost of the DVD discs themselves has come down greatly I
remember when the first DVD writers arrived they were well over £10
each, now I have seen adverts at around £1 each. With this unit you can
write both + and discs so there is no reason why you cannot buy
whichever is the best price. Using DVD for backup is a good use of the
media and something that several of the more recent production of
backup packages now support.
This is an easy to use, easy to install product at a reasonable price.
Link : http://www.theupgradestore.co.uk/mobile_computing/product_page.asp?id=Combi% then click on item 4