Well first of all I agree a TB20/21 is a delight to fly and I wouldn't want to miss a single hour I spent in it so far
TB20? Any day!
However from a renters point of view:
Even if the undercarriage and the turbo can be hassle when it comes to maintenance it is not really your business... And if you bring a Turbo Arrow up to a decent altitude (lets say FL100 or higher) TAS will be close to a TB20 but the hourly rate is way cheaper...