CHARON
+ Commercial-grade product.  Proper operation of VMS and other operating systems are tested for each product release.
+ Certified by HP as being a true emulation of a VAX or Alpha.
+ Support for user's Q-bus hardware is available.  (VAX only)
+ Installation, configuration, and migration can be contracted on a turn-key basis from
+ Annual support contracts and periodic product updates are available.
+ User training is available.
+ Accelerated CPU Emulation (ACE), which makes the product up to 4 times faster.
+ Physical SCSI drives are supported, including disk arrays and tapes.

Open Source
+ Can be downloaded from the Internet.
+ Source code is available.
- Not necessarily intended for commercial use.
- Installation, configuration, and migration are the responsibility of the user.  This can be contracted from Quayle Consulting.
- No support for Q-bus hardware.
- VAXeln operation not tested.
- Not certified by HP as being a true emulation of a VAX or Alpha.
- No training or support are available.
- No support for physical devices, especially magnetic tapes.