Go with the double spear model, if you need to move a hay ring or feed bunk while you are feeding cows the double spear will work better and you won't have to make a trip back to get the pallet forks.  Also the double spears give you much better control of the bale when moving it, once it's on there it won't move at all where with a single spear it will rock back and forth some.  This spear is one I just built for a customer and it's patterned after one I built for dad a few years ago, the guy saw it and wanted to know where dad got it.  They have a second set of spear sleeves so they can be moved up, that gives them a little extra reach for stacking bales 3 high if we ever want to or a second set of spears could be added for moving big square bales two or three high.  The back guard on them is 4' tall to prevent a bale from coming over the back plus it lets you see what angle the spears are at when you have them down low and can't see the spears themselves, our other loader spear is just tall enough for the loader mounts but when I get a chance to get them back in the shop I'm going to add extensions to it like this one has. 

This is the fourth loader spear I have built, the first one was a single spear which I later converted to a double spear then started over and have eventually settled on this design and haven't found anything I want to change about them yet.  The only change I want to make on the next set is to build about a 15 bushel hopper into the back with a hydrualic drive discharge auger so we can feed grain and hay at the same time without dragging buckets or bags around.