We have used #25 chain for years for our 6WD drive train with good reliability. The chain itself is very strong, like 700+ pound breaking strength, and is, of course, much lighter than #35 chain. Also, it allows us to get more reduction between the transmission output and the wheels than is possible with larger chain.
Good alignment is much more important than with #35 chain, and you need to have adequate wrap on smallish sprockets. We use a single chain around a transmission output sprocket, a tensioner, and the three wheel sprockets. Some of our machines have had only about 90 degrees of wrap on a 19 or 20 tooth transmission output sprocket, and the chain needs to be pretty tight or it can slip, not a good thing. The bottom line is that #25 chain will work for most applications on our machines, but everything needs to be more precise than with larger chain, including sprocket alignment, lack of wobble, and lack of runout of the sprockets.