Bogaievoli,
Welcome to the forum and welcome to the tractor search process. If you are like many of us, figuring out what to buy will be harder than half of the jobs you will use it for./w3tcompact/icons/smile.gif Being that you are brand new to the tractor world, I would suggest that a great starting point is the book authored by the founder of this forum. It covers the basics about tractors and implements as well as offers many buying and safety tips. If you go to the home page there is a banner that will lead you to information about the book so you can see if it would be of interest to you.
Another wealth of information can be found by doing some searches here on the forum. I will warn you that it can take more than a few minutes to read even part of what is available.
If I understand you correctly, you do not plan on using the tractor for finish mowing. If that is the case, you have already narrowed things down, which is good. Your question as to reliability is not too hard. Both of the brands you have looked at already as well as several others have great reliability and longevity. For the most part diesel compact tractor are pretty much trouble free if the normal maintenance procedures are followed.
Safety is a harder question to answer. There is no doubt that tractors on hills can be dangerous if not used correctly. Many of us live on hilly land so you can do it safely by following certain precautions. Again, reading through the Safety category on the forum will give you a great deal of information.
Keep asking questions as they come to you. You will find many knowledgeable people willing to help here. The more information you can share about the projects you foresee and the grade of your land the better. It really helps when offering specific recommendations on tractor size and implements needed.
Good luck and keep us posted.
MarkV