When it comes to steamrollers, a smaller pipe is easier to hold and smoke with. The larger steamrollers are a two-handed affair. You may need to actually use your palm to cover the carb cap on some large steamroller pipes. But if you want a massive hit, the larger pipes may be optimal for you.
It is important to note that there is a definite learning curve when smoking with a steamroller. If you are a beginner smoker, it may be best to have a few sessions with an expert steamroller smoker in order to learn the ropes. Or opt for the small pipe to get your skills up before moving to the larger pipe.