I've treid Bochs, it's geared towards the techhead like me, but even I gave up tweaking it to gain more speed, it's slow as hell and this is on an Athlon XP 2000+ machine
As for Virtual PC, I've tried out v4.xx and it seemed to be much faster then Bochs was and not as much tweaking involved. All I did however was to create a virtual 1GB hard file, format it and install MS-DOS 6.22 which worked just fine.
Moral of the story, well I've not tried them all out either but since I have a dedicated DOS box for just playing old dos games, well this is good enough for me. It's nice having a KVM switchbox to connect all these machines to one monitor, keyboard and mouse