I think there is general confusion in terminology here. When the topic of pick the team was brought up (by an American no doubt) it was meant in the context of, "what criteria should I have for selecting the 18 players I am allowed to keep on my roster" ie: the entire team.
The Welshman (who I'm guessing is from the UK) must be inturpreting "picking the team" as in picking the starting 11. From my time in Europe, "the team" referes to the starting 11.
Furthure more, in most instances outside the USA, once a sub is replaced, he's no longer available and often there are limits to the number of subs that can be made. For instance, the Liverpool Classic, allows 20 players on the tournament roster, but only 16 of whom may be listed as "available" for a particular game. Of the 16, 11 start, and 3 may be used as a sub, leaving 2 boys on the bench for the entire game-and Four boys (or girls) that don't even dress.
The Gothia Cup has no limit on tournament roster size, but allows only 16 players per game (but those 16 may be different for each tournament game).
Furthermore, many leagues have an "A" team, a "B" team, and so on. the players can move between A and B or even C on a weekly or even daily basis. Thus, the players the comprise the "team" for each game can be vastly differnt
So it is clear to me, that the term picking the team, is different for USA and the rest of the World.
To formulate your roster in the USA, it is wise to pick the players with the most skill and technical ability. Tactical awareness is also key.
Outside the USA, picking a variety of players will give you more options. When you are picking your roster for a match, or even your starting 11, your opposition may be taken into account.
