Hi Westva,
WARNING - I sell Grillo machines new and buy used BCS machines to rebuild and sell. Take this into consideration when reading my advice.
They're very similar machines. BCS is the largest manufacturer of walk behind tractors in Italy, Grillo is the second. They've both been building these machines at least 50 years and actually worked together for the late 60 to the early 80's. In the unlikely event that you ever see a BCS 755 for sale, it's a Grillo 131 painted blue. Grillo was actually the first to come up with the idea of multiple tools off one engine. Before they started working together, BCS only made purpose built sickle mowers. As far as staying power, they're matched.
The BCS 853 is a very nice machine. I have its predecessor as my primary garden tractor - an 850 diesel. It has a few advantages over the Grillo 107d The biggest advantage is more horsepower. This means you can put larger attachments on the BCS. It also has a lot more name recognition. BCS has been imported in one form or another since 1975. Grillo has been here since 2005. 30 years longer to embed into the US consumers consciousness.
They also have a much larger dealer network, BUT that doesn't necessarily mean anything. I recently had a fellow bring in a 716 that had been through two local BCS dealerships and a Non-BCS dealership and still had problems. Though I'm not a BCS dealer, I had the problems fixed in short order. He'll never go to a BCS dealer again. I also fixed a guy's 850 he just bought "in perfect working order" from a third BCS dealership a little further away. It had three rather major problems with it that cost him 20 bucks in parts. He'll never take it to a BCS dealership again.
The Grillo has a few advantages over the BCS. First is a lower price point. Joel is THE importer for Grillo. You buy direct from him or you buy from one of his dealers. BCS is imported through BCS America. They get a cut. They sell them through distributers. They get a cut. The distributors sell them to the dealers. They get a cut. Everything from the Grillo tractor to the Grillo implements to the Grillo service parts are cheaper.
The Grillo also has a better designed clutch. It's serviceable and can be rebuilt for about 50 bucks. BCS's clutch is nonserviceable and has to be replaced for $250. Yes, they can be broken. More so, BCS's clutch has a bad habit of sticking. They tell you right off the bat (if the dealer's any good) that you need to leave the clutch disengaged when not in use or it will be seized by the next time you use it. Unseizing them requires taking the engine off the tractor, taking the clutch off the engine, and squeezing it the a vise. About half an hour for someone who knows what they're doing.
Grillo's biggest advantage is Joel Dufour at Earth Tools in Owenton Kentucky. He's forgotten more than I know about both BCS and Grillo. He knows more about BCS than most of the fellows AT BCS America. With him running the importation of Grillo machines, you can bet your bottom dollar he'll get what is needed for the US market, not just what they want a dealer to sell.
As far as used implements, many older rear mount BCS implements and the sickle mowers will bolt directly to the Grillo with no adaptor. As I mentioned, BCS and Grillo worked together for a long time. They are very similar machines. Newer rear mount attachments will also bolt right up to the Grillo with a $60 adaptor. The Grillo turns the the opposite direction when in front mount mode, so the only front mount attachment that will work is a sickle mower. Snowblowers and rotary mowers will turn opposite and not work. Blowers can be adapted by flipping the gearbox, but it's just better to buy what you need in that case.
From what you mentioned for desired attachments, I think you'd do fine with the 107d, unless you want the wider implements.
