Pace is right but if it is only to do your MEP the 1 will work just fine. If, on the other hand, you are thinking of flying the same aircraft after your MEP I would think again unless it is an exceptional example.
Mind you even for the MEP part you will be sitting in the thing for at least 6 hours so if it is an old dog the price should be reflective.
If they have something else reasonable for hire dont forget you will probably need a couple of hours to convert to the "new" type so money saved on the 1 will not necessarily be money saved in the long run but, on the other hand, you will have the experience of two different aircraft.