Justy -This is why I wish deere had more options.
If deere had a x300 k46.
And a deere x300 gear.
I wouldn't even hesitate on the decision between the two. Hydro would be great for mowing, if it lasted. But I would choose the x300 geared, because chances are. It's going to tow and push snow, pull a landscape trailer. It will suck for mowing, but would have longevity. That would be more important too me than speed mowing.
I went to the big boxes for a sanity check and found (1) tractor a bit over $3K that has a K58 unit - marginally better than a K46 or K57. But the rest of the tractor sucked so bad I'd put a grand into mine in a minute.
The dealer said they have changed oil in older K46's with 20W50 Synthetic and gave them another lease on life. That's an option too... Deere recommends not changing it because it's a chore and most of John Q. Public would do more harm than good. And they like selling transaxles too. In my case pardon the pun, if the case seals are leaking when it goes in the tranny will be changed. If not I'll take the gamble on the oil change. A brand new K46 OEM unit dealer installed only has a 90 day warranty be it from Tuff Torq direct or from the JD dealer so nothing to lose there. Mine is going on 10 years old. So my old argument stands - anything that will kill a K46 will eventually do in a K57 or K58.