Just because there are four mediocre teams in the NL West that can win that division, doesn't mean it's strong.. The White Sox and Blue Jays would win that division, handedly.. They'll only get one playoff team this year, most likely, and that team will get knocked out in the first round.
The NL Central also has four teams that could legitimately win that division, does that make that division better too? Hell, the NL as a whole has more teams that could make the playoffs since the AL Playoff picture is before the season set at almost 6 or 7 teams, I'd say.. It's a lot more wide open in the NL, which means, more teams will be in the hunt.
AL Playoff Contenders:
Boston, New York, Detroit, Cleveland, Seattle, Los Angeles...
That doesn't mean teams like Chicago and Toronto aren't good, it's just that they are very long shots to make the playoffs.. When you list the NL playoff contenders its a far longer list...
NL Playoff Contenders:
New York, Atlanta, Philadelphia, Chicago, Milwaukee, St. Louis, Cincinnati, Arizona, Colorado, San Diego, Los Angeles..
That doesn't mean the NL is better than the AL, either, as can be told by interleague records and all-star game results.