Scag dealer here says they cut small saplings all the time. My dad bought a DR and unless you've used one before you might want to try it first. Those things can be a beast. In fact anything the DR wouldn't be a beast on, the Scag can probably handle.
I would try the Scag first and save my money,or rent a tractor to cut it down the first time. If it's just grass cut it high and take down a little at time and not one big bite all at once.
Snapper S50x 36" Deck
Shindaiwa EB212 Blower