There are FOUR questions you need answer to make an informed decision:
1. Do you need VT (variable temperature) capability? If yes, A600/F500/Hg400
2. Is this a heteronuclear experiment (other than 1H and 13C)? If yes, A600/Au400/F500/Hg400
3. Do you need immediate access to instruments? If yes, Ag500/Au400/I500
4. What kind of sensitivity do you need?
For most experiments we do, proton sensitivity is most important factor to consider, except 1D carbon, which depends on the 13C sensitivity of the probe. For specifications on each of our instruments, please refer to “NMR Instruments” section.
Here is a general ranking of 1H sensitivity: HCN600 >> Ag500 > A600 > F500 > Au400 > I500 > Hg400
ranking of 13C sensitivity: Ag500 >> F500 = A600 > HCN600 = I500 = Au400 = Hg400