We bought James last night while we already had battery operated Percy. James does not run as well on Melissa and Doug train track as he does on original Thomas train track. He is also more sensitive going around curves. It seems to be the middle wheel. As the middle wheel is loose and can float up and down, it seems to cause the train to get stuck at certain points along the track even while running on only original Thomas train track. Percy has no problems on either train tracks and never gets stuck.James does seem faster than Percy but that could be due to having a newer battery.