I think there is some rose tinted glasses being wearing with some of you saying a pacer is better than a 150.
The main advantage of a pacer I can think of, is the environment is much lighter with the larger window to metal ratio they have.
The main comparative disadvantage of pacers compared to sprinters is that they have less seats, there is no separate cab door for opening/closing doors, the doors themselves are relatively slow to open and cause internal space to be eaten up in opening/closing them.
Others have said they are more reliable, and I believe they also have better acceleration.
150s are simply better than pacers in most ways.
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The Class 141s had separate crew slam doors like the 150/1s, but they were abandoned on the 142 to make best use of space.