I am choosing the 1655 over the 1670.
Here are some positive reasons why I prefer the 1655...
1) Compatibility with QSuite/SB/OS/WOPC & MCSE
2) 3 firmware versions already released, tested & commented on.
3) Ability to Scan Media using CDSpeed/Nero CD-DVD Speed/DVDInfo Pro.
4) Very Good Writing Quality on SL, as well as, DL
5) LightScribe Capable, if you want it.
Here are some negative reasons why I am letting go of my 1670...
1) High Jitter, TOO High
2) Inability to burn currently at 12X
3) Not capable of achieving the same quality burn using the same media that I use on my 1655 at the same burn speed.
4) Cannot currently scan....perhaps never, with the Panasonic Chipset.
5) Not currently compatible with QSuite & it's tools.
6) Does not burn Quality DL media well, or as good as my 1655 will burn DL media at the same speed.
I've enclosed some DL burns on both the 1655 & 1670 for comparison. The 1st two scans are from my 1655 burning MKM 001 DL@4X, SB=off,OS=off, WOPC=on
The 3rd Scan is of my 1670 Burn of the same media at 4X.
My results may be unique to my burners/system/firmware/media. Your experience may differ. Trust your own experience.