I've spent some time looking at them. I have some property that has some places nothing on 4 tires will go (and come back). The L35 would be stuck and the BX you'd have to jump off of before the stack (rops) went under the waves (mud). Excavators are wonderful for their uses, can be unbelievably expensive to repair, especially if someone swings it into a solid object and damages the pivot mechanism.
Yes Kubota makes some nice ones, KX91 121 etc. There are a lot of excavators out there, used ones for sale. Many of these have been brought over from Japan. Although it isn't as bad as "grey market" Ag tractors parts wise, many of the excavators are different if not a US model. I looked at a Komatsu, local dealer said he can get parts fine if I find a parts manual, which he says will be in Japanese. I'm sure there are some heads-up dealers out there that have acquired the books themselves, but it can be a concern. I've heard contractors steer clear of them so resale may be a concern. Check with the dealer before buying on this. Most of the ones in my needed size 7K-9K lbs have rubber tracks, which I am a bit nervous about in the woods. New tracks can be $2K per side! They are used in Japan on the roads. Contractors here mainly use the little ones with rubber tracks for landscaping etc, can go over curbs etc and across lawns, where a steel track would throw up a rooster tail of sod and cement behind it. So resale might be a problem with a steel track machine. I have rented some bigger units 28K lbs. Once you see use one you'll see the benefits, being able to infinitely position the machine left right, back forward and swing the whole thing around it made me feel my tractor mounted backhoe was ridiculously imcompetent. Of course if you want to move dirt or go anywhere the excavators move at about 2mph top speed and that's a BOUNCY ride! They will go up a good incline, some have rather interesting hydraulic or manual parking locks even though the transmissions seem to be like an HST.
If you are daring, you might consider an auction, the biggest company that is running auctions all over the country is Ritchie Bros, last one I went to had literally hundreds of dozers, loaders, excavators 5000lb to 100,000+lbs. I've wondered though why someone would sell something at a no-reserve auction if the item is worth anything. I saw some big pieces of OPERATING equipment GO FOR PEANUTS. Of course I didn't go up on the runway and see what they left behind...oil, parts etc. I'm sure a lot of them are "mechanics specials."
The hoe on an excavator size for size is usually much stronger than an AG tractor when you compare the digging force specs, and they usually have much longer reach. Most of the small ones also have a unique feature in addition to the regular backhoe functions, the boom also swings separately from the "house" or the boom has a pivot in the middle. This allows you the benefits of the old "offset hoes" that you could get on tractors without the drawback of always having an offset hoe. You can dig a straight line towards you with the hoe all the way to the right or left of the machine. If you wanted to dig a rectangular hole 6 x 6 feet this is perfect for that, or digging along foundations or anywhere where clearance is tight.
You also want to get the drop down dozer blade. Although you aren't going to be doing much land clearing with it being a top heavy structure, and you don't want branches and stuff coming up at your face, the blade allows you to make a flat spot to sit and dig. These machines are sensitive to ground conditions and you'll do a lot less time rocking back and forth with a nice flat spot. Putting the blade down while digging also makes the unit much more stable. You can usually only get a drop down blade up to about an 18,000 machine.
A thumb runs $1500-$3000 and is again a great tool if you are doing any woods working. Some machines are already plumbed for the which can save $$$.
One of the first times I rented a bigger machine I wasn't as careful dressing up my working spot. I was ended up rocking back and forth on a tough old root from an old growth tree that had been cut 80 years ago. Didn't figure I'd be there that long so just went slower. I was redigging a ditch that I had previously dug with my backhoe. I was concerned about the sides of the ditch and dug sitting to one side of the ditch. In hind sight I probably should have straddled it or filled it in and started over (best).
Somehow those metal tracks found the root a bit slippery and when I swung the hoe back instead of the hoe coming back the excavator just moved sideways, dropping one track into the ditch. For a second there Mr. Macho was considering calling for his mommy. Probably normal operating angle for a professional. Too bad I didn't have a Tiltmeter in it, I would have enjoyed watching it swing over as I mentally calculated the repair costs to the machine as it took me on a fun ride.
I don't know which is better, a "tractor hoe" or a trackhoe. They both have uses and drawbacks. One fellow on this board has said he has an L35 a BX and KX121 or 161 I think. Well, I'm 2/3 of the way there!
This is a picture of a picture so my apologies for the quality.
http://www.oldcarparts.mygarage.com/images/excavator.jpg