Think of this scenario: the best war buff/debuff is the 30% slower one and is 20,000 tokens. The smaller buff 10,000 hp to heroes is 2,000 tokens. For every surviving tower in a successful defense a guild gets 500 tokens per tower remaining and a guild defense win in war is 1,000 tokens. If a guild wins an attack that guild will get 1,000 tokens.
If you have a 25 opted in for war guild defending against a 50 opted in for war guild the 25 opted in will have no surviving lines left yielding no tokens for surviving line ups and no tokens for not winning a defense. Once the 25 guild attacks the 50 guild they may win the attack for 1,000 tokens or lose and get nothing. The 50 guild will get a minimum of 12,500 tokens for 25 towers standing plus 500 tokens for every extra surviving tower and 1,000 tokens if they won the defense.
The 50 guild will yield plenty of tokens in a war week to buy the big buff, and the 25 guild won't have made enough so will have to buy the cheaper one. The smaller guild will have to recruit and communicate more as well as hoard more tokens so they can climb the ranks better.
Also, of course, rewards need to be worth it to want players to climb the ranks. Bragging rights just don't seem to cut it these days.