I have one bent that has a small 20" front and a 26" rear (low weight at less than 30lb). At high speed I find this bike is somewhat wobbly and requires full attention to steer. The bike also does not handle well under a heavy packed load, say for touring but OK for short communting.
My other bike has dual 26" wheels which I find much better at higher speeds, more stable under load (heavier bike at nearly 20kg) and I can get good road touring slicks for it. It saves on on taking extra tubes and tires of different sizes when riding.
There are also bents out there with 24" and 700 (27")size wheels. From what I understand the larger the wheel usually the more stable the ride, higher speeds. From what I've experienced so far the large wheel bent I have handles much better than my small wheel type.
Does this confuse you more?