I would go for Ten Hag over Poch but I'm not sure its really this cut-and-dried.
The counter-argument to this bit about a good coach versus an exceptional one is that you don't actually need an exceptional manager to win the league, we've just been going through a bizarre period (that is soon to end) where the two best managers of the last 15 years have been in the league and also at the head of teams that are probably in top five all time in the PL, so our perspective is a little skewed by their level.
In the immediate pre-Guardiola/Klopp period, the title was won by Antonio Conte, Claudio Ranieri, late stage Jose Mourinho, Manuel Pelligrini, Fergie, and Roberto Mancini. Only Ferguson and maybe Conte could be termed exceptional.
It's great to have an exceptional manager, but its also important to have a good one. With a good manager you can win the title if you have enough resources and get enough other things right as a club (obviously that last part has been a struggle for United recently). If you don't have even a good manager - and I would say that Ole is a prime example of this - then you don't have a prayer really.
I would still go with Ten Hag because I'm pretty confident that he is at least a good manager, with a small chance of being exceptional. But I really disagree with the notion that hiring Poch means never ever winning anything, especially given that United's next rebuilding cycle (under any manager) is going to take a couple years anyway and by that time Guardiola and Klopp are quite likely to be gone.
Your point - as I take it - is fair enough: the landscape changes all the time, and it is certainly possible that a less-than-exceptional manager
could win the Premier League once Pep and/or Klopp is gone - or simply when said landscape has changed a bit.
However...the Premier League is currently going from strength to strength in terms of attracting the best of the best - players and managers. It seems unlikely to change for the time being - football moves in cycles, on all sorts of levels, but currently the PL is both a) very strong and b) still on the rise, really, certainly not in decline.
United - meanwhile - are certainly not very strong. Nor on the rise - if we are, it's very well hidden.
For us, here and now, I maintain that it makes far more sense to gamble on a potentially brilliant manager (who has something beyond the ordinary - an X factor, if you will) - rather than going for someone who would be good enough if our relative standing compared to the competition (City, Liverpool, Chelsea) was anything like it used to be.
The reality is we
might have an edge on Liverpool in terms of resources - but nothing indicates we're better run than them. And they have an exceptionally good manager.
We don't have any kind of edge on City in terms of resources - and they also have an exceptionally good manager.
We might also have an edge on Chelsea in terms of resources (let's disregard the most recent developments - we don't know where that will lead eventually) - but they also have a manager who is, at least, well beyond just "good".
There is absolutely nothing which - at the moment - indicates that United, in our current state, will have a snowflake's chance in hell of going up against those three teams with Pochettino in charge next season.
So, based on your reasoning (which I don't disagree with, as such) - if we do hire him, we have to rely on factors beyond him. We need our rivals to become weaker, basically.
We might even need the league itself to weaken, or more precisely decline in overall standing or status - making it less likely that City and/or Liverpool (nevermind Chelsea...or other teams, Newcastle before too long) will attract an exceptional manager once Pep/Klopp moves on.
In short - the idea that United can win the league with a good, but not particularly brilliant, manager in the foreseeable future seems very unlikely to me.
You could say that it's unlikely regardless of who we end up hiring - but that sort of reinforces the point: if we are to stand a chance, it seems likely that we'd need something (someone) out of the ordinary to do so.
