My X739 isn't noisy, neither in transmission nor engine. No whine except under very heavy load. The AWD with AWS is simply awesome. Outstanding traction, maneuverability, and won't tear your grass. Nothing like it by any manufacturer. There is no garden tractor with the sophistication or features of these X700's. The Simplicities are nice, but they don't have the engineering that JD does when it comes to the range of attachments, ease of use, and performance. IMHO John Deere has no competition in this class. No one is close. If spending the kind of money that can purchase an X738, it would be a mistake to buy anything else in the same class.
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This is one area where I do bleed JD green. 19+ years on my 425 (a predecessor to the X-series) and I still love that old girl; runs like the day I bought her. Selling her this spring and it will be an emotional separation when she goes.