Terminal problems at IAH
 

I fly from McAllen,TX (MFE?) to California and to DC several times a year. This entails changing at IAH. For years the flight from McAllen to Houston has been full. Can't remember when there was an empty seat. But suddenly CO has started flying those little Brazilian planes (Embraers>) which obviously carry fewer passengers. This means flying into Terminal B and taking a bus from the plane to the terminal and then using the tram to the terminal where my connection will be, often D. Last time I went to DC coming back I had been scheduled on a 737 connection between Houston and McAllen with a 30-minute wait period. Although the 737 wasn't in B it was way the other end of C, and I barely made the connection. My question is twofold: 1) Why is CO using small planes for the McAllen connection when it is patently a good business source, and 2) What governs connection wait times? I am an old lady, and while I try to get an electric cart, sometimes it takes a while to do so..