There is nothing wrong with either of them for the price, I would personally go with the JD 140, Or a better bet would be to try to find a good used mower, A JD 345 or X345 would be a great mower for that price range.

As for blade engagement, I know one's a lever and one's a button or switch (switch on the old Cub Cadet). Is there any difference in the reliability or belt life? Any difference in ease of use? With the lever, do you have to stop the mower to engage the blades? Thanks in advance.

personally, I would get a machine that was designed/proven to work well in southern climes while being simple to care for and store in off season, Check out the trusty Snapper 30" Rear Engine Rider - there's still a few left at dealers here and there...

2) diff between sw and lever for deck blade engagement is electrical and mechanical. 1.A magnetic clutch assy is switched on and off via a switch on the console. 2. a lever or handle is used to move a series of other levers/cables/links in such a way as to tighten a belt running from the engine crankshaft to the deck blades pulleys.
option #1 is much more expensive, much more convenient and less reliable in general
option #2 is less expensive, slightly less convenient and more reliable in general
with either option, you can engage/disengage at any in general
but -as with any piece of powered outdoor equipment, always check your operator's manual for safety instructions