Making the best choice probably boils down to which one is in better overall condition. Either one could be a good choice for mowing, etc., but let's face it, these are 40-50 year old machines, and there have probably been things fixed on them previously, and certainly, there will be more needing fixed in the future. Perhaps you know someone who is familiar with tractors who can give them an expert "tire kicking". Otherwise, it's a roll of the dice, but don't be shocked if either one needs some TLC to keep it running.
Also, does either machine have the "gardening" attachments, particularly cultivators? Such attachments were built specifically for each tractor back when these models were built, unlike more modern equipment that use standardized, universal-fit implements. Lacking attachments, you may be limited to mowing with either of these.
By the way, welcome to TBN. Keep asking questions... there are lots of knowledeable people with answers.