Subaru makes a quality product. That being said, I have never used a mower machine with a Subaru engine on it personally. I do know that Gravely researches the heck out of their line of gear. With a 3 year warranty, you should be good to mow. OBTW, they will give you a loaner if they can't fix your problem within 24 hours. It's their "no down time" guarantee.
Tons of excellent choices out there to be sure but some of my favorite features of the XD3 are the variable speed up to 3.2 MPH, the single lever deck lift mechanism and the 4 inch tall deck interior. This looks like a quality product, represented by a proven company. The step up from that little mower is the classic LM series which is 550.00. Or the Pro 21 XD, they have Kawi or Honda engine choices, They are 950.00. My advice is to try and use a dealer for your gear purchase. Find one in your area and do your due diligence in selecting them. Dealers that appreciate your business will save the day more times than not. Thats been my experience and I always had to learn the hard way. I wish I had these forums 20 years ago lol.
My top choices from 1st to last respectively are: Gravely, Dixie Chopper, Scag, Exmark, Hustler, Big Dog, Toro, John Deer and Cub Cadet or Husqavarna. The Gravely being my favorite over all because of cost, service, quality, user friendliness (easy to maintain) and manufacturer warranty.
I am going to get the XD3 because of some tight spots on my land and around the house itself. I am sick of leaning over my weed eater to do it. Great gear does not make you lazy it just opens your eyes to the options available lol.
I hope my 2 cents help you out.