I was faced with the same dilemma: 23 years of home video in 4 different formats! In the end, I just borrowed machines for the formats I no longer have and just put all the tapes on to a hard disk using Plextor, backed it up, unedited on to DVD's, before returning the machines.
I then treated editing as an, as and when I feel like it, project. But it's been great fun for the whole house, breaking it down in to usable bites: coming across forgotten and faintly remembered events.
Your professional transfer service can't do that editing and transferring is the easy bit, you just set the tapes running and go away, whilst they read on to your hard disk.
N.B. Don't forgrt to edit out the bits with your first three wives/girlfriends before letting the family look over your shoulder!
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Politics and Ideology: Not my bag