My dad was ordained in the Wesleyan Methodist denom. His best friend was ordained in the Free Methodist church. I remember them bantering back and forth about congregationalist vs the more episcopal government styles of government. Dad said the 2 denoms had been in talks on and off since about 1900 on combining the 2 groups as their doctrinal slants were virtually identical - except for the style of church government. They could never get past that point.
Similar to TEC, the UMC, and in a smaller part the other "seven sisters". Doctrinally VERY similar. But a handful of caveats with each one that is significant enough to prevent any sort of a 'merger'. Governance is one of them.
To add to the great stuff RomansFiveEight has said, the appointment system is one of the reasons that the UMC has been able to maintain smaller churches in many cases when congregationalist churches have closed their doors.
Many small UMC pastors share a pastor in a single "charge" led by one pastor. So a small church that can't afford a full-time pastor shares that pastor with one or more other churches that also can't afford a full-time pastor. Those churches are able to get pastoral leadership while pastors can maintain full-time ministry.
Having pastored both in a congregationalist system and now in the UMC system, I believe the appointment system, while not perfect, has a much better chance of offering matches between the gifts and graces of the pastor and the church and getting the most even deployment o pastors.
Also one of the side effects of congregational systems is that it basically encourages the pastor to ladder climb from one church to another for a big size or a bigger salary. When you make getting the right pastor for the right church the rule rather than the pastor picking her/his own churches you get a fairer distribution of leadership.
You are also less likely to get pastors who are in it for the prestige or the money when someone else appoints you to a church.
Thanks for the correct on 'church wide voting', I should've added that. Our last "church conference" (for those that don't know; that's the term for a church wide vote; the District Superintendent presides over it) was ten years ago to decide whether or not to purchase a new home from a developer and use it as a parsonage; as the current parsonage was aging, in need of repairs and updating, and was located right next door to the church, practically an attached building. The Pastor at the time had small children and folks in the church, wanting to take care of him and his family, didn't like the idea of those kids growing up on Main Street in a commercially zoned part of town blocks away from any other houses, with no yard (a parking lot on one side; a road on the other side. Buildings on the left and right; the church and a bar!) So they voted, church-wide, to spend the money to buy and build the parsonage. My wife and I sure are appreciative of that decision!
But that was the last time. All other issues, including improvements and renovations, have been left up to the appropriate board. Like most UM churches, we operate with an "ad council" made up of representatives of sub-committees. The Trustees, for example, manage the building and property. They have a budget for the year. If something falls outside of that budget (large, unexpected repair or an opportunity comes up for a renovation, last year we had some storm damage to our room and our trustees thought that would be a great time to install an all new roof, since part of it would be funded with insurance money) then they present that to the ad council. But it's representatives of the congregation, not the WHOLE congregation being mobilized on every vote.
Our Bishop wrote a book, "Just say Yes!" in which he criticized some local church governments (including many UM churches!) saying "They have several committees that can say no, but not any one of them have the power to say 'yes'". This is even MORE true of churches that mobilize a vote for everything. The church I "came from", for example, if any one person decided they didn't like something, the rest would follow along. The feeling was if we didn't unanimously say "yes", then it was a "no". That's a great system for juries in a criminal trial; but not a great system for the church. Sometimes you have to make decisions that aren't every single persons favorite.
I serve one of those two-point charges, and it works very well. I'm sure each church would rather have a sole-Pastor. But they can't afford that. If they were congregational, they'd have to find some bi-vocational Pastor, perhaps one that wasn't really qualified or even felt called to serve in that role (A church near me, for the last TEN YEARS, has had a lay person who has a full time job 'filling in', who doesn't feel called to be a Pastor, doesn't want to be a Pastor, just preaches on Sunday until they finally GET a "Pastor"). What they DO get, is for sharing a portion of my salary (one church pays 2/3, the other pays 1/3), is a Pastor who is available for each church full time, can attend continuing education events, goes to conferences and seminars to better equip himself, can make those 1PM in the afternoon surgery hospital calls or those two in the morning emergency hospital calls, etc.
To be clear, bi-vocational ministry is a very valid form of ministry. I know some, and the workload they have is tremendous. They use all of their vacation time from their secular job to make things like continuing ed and annual conference, and vacation time from church to catch up on their secular job. It's incredible! But that model doesn't work in some churches, and thanks to our connectional system, they aren't forced into that model. Multi-point charges, I think, is a saving grace in the UMC.
I'd even like to see a return of circuits. Appoint a Pastor to 5 or 6 small churches, and empower and equip lay people to preach in the in-between. It does happen still, though it's rare. Usually, the Pastor preaches at two or three one week, then two or three the next week, with lay-people in between. But they are a full-time Pastor serving this clutch of churches, offering them pastoral care, leadership development, et al during the week; and that's the really important part they'd miss out on if they couldn't afford a Pastor.