I've always felt that the scenario where Olson and Reed compromise is guaranteed to lead to massive problems down the line, because of what the compromise is. Reed demands the SPA be put in charge of an agency that will be in charge of moderating labor disputes. That's the courts job (there was a supreme court case about a labor dispute fairly recently, so that sort of thing is clearly in their jurisdiction). So basically, Reed gets to set up a parallel justice system that is permanently under the control of his political party, which is such a flagrant violation of the constitution that there's going to be a reckoning about that at some point.
Compare that to the Long compromise, who demands a tax break (annoying and can be seen as pandering, but not illegal), and demands to be the head of a new senate subcommittee (the senate is allowed to make its own committees so again, annoying and can be seen as pandering, but not expressly illegal).
There's also the way each side reacts to it. Reed gets a compromise that allows his party to permanently rig the system so that they will win every labor dispute in the future, and his people are still rioting and striking throughout New York and Boston, there's an event that tells you how Reed is struggling to get his followers under control. Again, compare that with Long, who gets more modest concessions of a tax break and being the head of a senate subcommittee, and you get no further problems from the south. There's no event like Reed's where Long's people are rioting and he's struggling to get control over them.
The SPA is also the only party to throw a massive tantrum after the election. You get no Longist equivalent to the New Years Strike. The SPA is by far the most radicalized and out of control faction going into the civil war, and even if you compromise with them, with the nature of the compromise, their radicalization and the fact that they are the only faction where the explicit goal is a new form of government, I just can't see anything but further problems for the Progressives.