Pending DosFreak's CoreDuo investigation here are the trade-offs as I see them:
NTVDM:
Pros:
1.) Can do up to Video up to 800x600 very fast; 1024x768 slightly slower.
2.) The use of audio 'music card' selection of General MIDI allows the Direct Music MIDI sub-system of WinXP to use another thread external to the NTVDM's threads to handle this task.
3.) VDM Sound v2.1.0 handles the task of emulating a SB16 quite well in-game - only fails to give good sound during Intro Video cutscene digital output.
4.) Can use Yamaha MIDI softsynth S-YXG50 (v4.23.14 WDM) instead of Microsoft/Roland General MIDI softsynth.
Cons:
1.) Must use patched VGA.SYS for NVIDIA video adapters to get beyond VESA mode 0x101 (640x480x256color) and find way to prevent the WinXP file-protection system from restoring original VGA.SYS file.
2.) Limited to General MIDI as 'music' soundcard selction and the native WinXP SoundBlaster 2.0 or VDM Sound SB16 'digital' soundcard emulations.
3.) Must use MOUSE2KV.EXE to execute CDSHOCK.EXE with parameters properly set for desired playing resolution. Since Mouse2Kv is not dynamic, this causes problems with Mouse positioning when switching back to basic 320x200 resolution when using AutoMap function and when switching back from 320x200 to VESA 0x100 or 0x101 modes. Must position Mouse at co-ordinates 0,0 so no crash.
4.) The 320x400 Mode 'X' resolution variant very unstable in NTVDM environment. Crashes much of the time. Not really usable.
5.) Use of BIOS supported VESA 2.0 or 3.0 modes usually limited to 60Hz refresh - problem on CRTs, not on LCDs. Must hack BIOS to support >60Hz on most modern Video adapters.
Dosbox v0.65
Pros:
1.) Video at 320x200 guaranteed to work on emulated S3 video adapter. Can use scalers to help with lo-res output. Speed is good on fast PCs. Possiblity of hardware line-doubling on certain Dosbox builds. Refresh rate at native CRT/LCD rate unlike NTVDM.
2.) Audio selections more varied than NTVDM choices. Very good SBPRO 1 or SB16 emulation stereo emulation- no breakups. Can use same WinXP Direct Music MIDI or Yamaha MIDI as can the NTVDM solution.
3.) Only solution for being able to enjoy the Gravis Ultrasound specific customisations made by LookingGlass for SYSTEM SHOCK. Problem is lack of documentation on how to setup Gravis Ultrasound. Formal support was removed just before shipment of CD-enhanced version since the MILES Ultra.mdi and Ultra.dig drivers files were not ready. The included UMID files (which would required software TSR UltraMID) don't work. Possible to patch around driver names - then need undocumented CUSTOM.GUS file for use of 14 LookingGlass generated custom Gravis instrument patches.
4.) No problems with Mouse in any supported VGA or VESA video mode.
Cons:
1.) Current AMD and Intel processor speeds limit Video resolution to 320x200 for playable speed with S3 emulation. Other video resolutions operate in visible slow motion...
2.) Single threading model has resourse intensive audio emulation occasionally impacts on-screen action. Much of the blame might be on the MILES drivers which take a bit too much time as they are called as an ISR with interrupts disabled for the duration with some drivers.
3.) Hypertheaded INTEL processors usually require setting processor affinity in WinXP for Dosbox to a single processor - otherwise the WinXP dispatcher may switch virtual CPUs and you get an occasional 'hiccup' when pushing the CPU usage to high levels for performance in Dosbox. Might be similar on dual-core CPUs...
4.) Seems that Dosbox v0.65 using CORE=normal more stable than dynamic - results mixed. Lots of self-modifying code in SYSTEM SHOCK executable.
If CPUs get fast enough - Doxbox is your answer. To play in the newly unlocked 800x600 and 1024x768 (with 1280x1024 possible) you have to use the NTVDM solution.
For comparisons of the use of various soundcards for SYSTEM SHOCK (via AVI streaming or downloads), see my entries on this thread over on TTLG forums. Used Dosbox v0.65 soundcard emulation and real soundcards for comparisons in the AVI files.
Just my view,
dvwjr