My vote would be for the larger tractor and a different lawn mower for the yard, you can get a half way descent rider for way less than the cost of a mid or rear finish mower. And with the smaller mower you can get closer to trees the branches of the trees don't have to be trimed back so far, and the wife could possibley do the mowing if she likes my wife loves it and won't let me on the mower.
If you go smaller on the tractor and get turf tires you will also limit the amount of work you can do on the ballance of your property. As far as sharing impliments with your friend category 1 is category 1 the only difference could be the width of the tractor and the width of the equipment but they would still work as long as the tractors are relativley the same HP. And skidsteer QC is skidsteer QC they should all be able to connect up to each, now there could always the possibility of a small difference but I haven't heard of any as long as it isn't a JD that is.
As referenced previously make sure you look at all of the MFG's and find what fits you the best. Everyone here will try to push or recommend there favorite brand and they are all good, but what is good for someone else may not be good for you. And if you go by everyone elses opinion to buy a tractor you would have robbed yourself of the best part of buying a tractor the going out sitting on them driving them and in general just enjoying the whole experance! Oh well I have ranted way to much here!