I kinda despise that beam axle on the Beetles and Jettas. Handling never felt as secure and confident as the IRS. Within the capabilities of the car there is no benefit, that I can see, to the beam suspension for towing. BTW - yeah, '13 should be last year of solid beam, but on a change like that there can be a few that sneak through during the change over.
As far as towing the Tiguan has much the same rear suspension at the Beetle and Jetta and it is rated to tow decent amount. The Touareg has a rather large towing capacity and IRS.
Bonus - because of similarities between IRS versions there are plenty of options to swap (coils, shocks, bushings, etc.) to change behavior to your liking.