If you want DVD+R overburning (as in burning more than 4482MB, not to be confused with overspeeding which is burning faster than the media’s reated speed), then your only choices are BenQ 1650/1655 and Plextor PX-755/760.
Between the LiteOn 165H6S and 1635S I would buy the 165H6S because it’s the latest generation LiteOn. The only theoretical crossflashing I know of between recent LiteOn drives is 160P6S to 165P6S, but it’s not a good idea because the only difference is DVD-RAM capability in the 165P6S, but the 160P6S is or can be a 165P6S that failed DVD-RAM during factory testing!
A LiteOn 165H6S is the same as a 165P6S, except that the 165H6S also supports LightScribe.
If you need all your requirements fullfilled, I suggest you buy a BenQ 1650/1655 (the 1655 has LightScribe support). If you don’t need DVD+R overburning, then the LiteOn models are also good.
The only thing that I find disappointing with my LiteOn drive is the CD-R writing quality; there are other better drives for this purpose, such as NEC 3550/3551/4550/4551 or BenQ 1650/1655.
A review of 165P6SI have read over at CDRinfo suggest that the LiteOn 6S series may be even worse at CD-R burning than the 1635S.