Joining on base can be frustrating for the guy on downwind because in normal "rules of the air" you give way to the aircraft on the right, hence if you are on downwind you may not have anywhere to go to avoid the other aircraft depending on how soon you saw him. If you turned left, you're effectively cutting him off and may be shortening your circuit and if you turn right, you may have to turn quite sharp to avoid him.
The regs are the regs though and the base joiner is supposed to give way, but indeed it doesn't always work out for the best as you have found out!
Straight in approaches can be a little simpler to manage as whilst the other circuit traffic has right of way, the downwind traffic can easily extend if he is kind.