I looked through all the teams top prospects the other day and IMO they break down into 4 groups.
Group 1 are the teams like the Twins with elite talent and depth. Every team has 6+ top 100ish prospects and a premier player. Astros, Cubs, Red Sox, Twins and the Pirates.
Group 2 doesn't quite have the depth but has 4+ top 100 prospects. They also have some very intriguing players that could quickly become top 100 prospects. The Mets, Dodgers, Royals, Rays and Marlins fall into this category (though to be fair the Mets have Syndergaard and d'Arnaud who could be considered premier).
Group 3 teams either have 3-4 top 100 prospects, one might be elite, or 2-3 top 100 prospects but 2 of them are elite. This is the biggest group and includes the Indians, D-Backs, Rockies, Cards, Mariners, Rangers, Phillies, Reds, Blue Jays and the Nationals. The Cardinals could fit anywhere from 11-22. I'd put them somewhere in the middle because I don't think they have quite as much depth as some of the other systems.
Group 4 teams are just B. A. D. Let's say it all together, BAD. A's, Padres, Giants, Tigers, Braves, White Sox, Brewers and Angels.
I think you're selling the Mets system quite a bit short. They have 2 premier prospects in Syndergaard and d'Arnaud and a very nice pitcher in Montero. In addition Wilmer Flores, Steven Matz, Kevin Plawecki and Cesar Puello were all listed in the "Honorable Mention" section of Sickels top 75 list. They also have Dominic Smith who was their 1st round pick in 2013 and was considered the top prep bat of the draft. Dilson Herrera is an intriguing 2B prospect that has the tools to be ranked in the future.
The Royals have a much better system than the Cardinals as well. In addition to the 4 he mentions they also have Hunter Dozier and Sean Manaea from this years draft. Bubba Starling, if he can ever put his tools together, and Jorge Bonifacio are both intriguing. John Lamb has had injury problems but was a very good pitcher a few years ago.
I'd take the Mariner's Walker, Hultzen, Paxton, Peterson foursome over the Cardinals Taveras, Martinez, Wong, ??? (assuming Hultzen's injury isn't career ending). Though part of that is because I value pitchers much more than OF's and 2B.
The Indians I'll give you, though I aboslutely LOVE Lindor. I'd trade Sano or Buxton for Lindor. Boom. Done.
My 3 "top of the rotation" possibilities for the Pirates didn't include Kingham, btw. Taillon, Glasnow and Heredia are the 3 I was talking about. I think it's too early to judge McGuire or Meadows based on the few AB's they got this season.
It's not too early to judge McGuire. I didn't like him that much in the draft and I still don't. Meadows is a different story.
To continue the discussion with some minutia because that is fun sometimes, I don't disagree about Heredia, his stats have not backed up the scouts so far. That doesn't mean they won't in the future though. Interestingly he gives up few hits which compensates for his wildness. I'm not sure that is sustainable but it is intriguing.
The Twins have some young arms with a lot of potential; Stewart, Gonsalves, Thorpe, Felix, Rosario, Landa; but they are so far away it is hard to compare them to AA and AAA players. In addition I don't know the Pirates system well enough to know how well their A- and Rk ball pitchers are thought of.
If we limit ourselves to the more well known commodities, say A-ball and above, the Pirates have the better pitchers, IMO. Taillon is considered better than Meyer, though when it's all said and done I wouldn't be surprised if Meyer is the better pither. Glasnow is clearly a better prospect than Berrios and Kingham is better than May. After that the Twins have a bunch of guys with back end ceilings while the Pirates have a mid-rotation guy in Kyle McPherson, assuming he is healthy. The Twins might have the better young guys, again I don't know the Pirates' system well enough to comment either way, but above rookie ball it is hard to argue against the Pirates.
As for McGuire and Meadows I said it's too early to judge based on the AB's they got this season. It is just a small sample size and it means little. I think it's fair to judge them on their scouting reports at this point and if you disliked McGuire before the draft well, he has done little to change opinions one way or the other.
I don't think the Twins were wrong to take Stewart but I do think that in a few years, I could see Meadows being the best player and a lot of teams kicking themselves over passing on him. It seemed (from things like minorleagueball) that a lot of people were thinking he was a "boring" pick, didn't have the upside of Frazier, small HS, slow to the majors, etc.
Sickles preferred Frazier. I know that... I'll have to disagree there.
Mayo and Callis over at mlb.com picked which team they each thought had the best farm system. Callis went with the obvious answer the Astros while Mayo.....well he does what Mayo does and picked the pirates for arguments sake. Last week he picked Bryant over Sano as the best 3B prospect in the game even though he has Sano ranked higher. Here is a link to his article on why the pirates have the best farm:
Pipeline Perspectives: Pittsburgh Pirates have baseball's top farm system | MLB.com: News