Let's assume that game money, tokens and boosters are the only 3 factors that will affect your decision. You can only buy 1 of the 2.
1/ 18 years old very fast trainer, quality ending in 4/9, no SA, cost <5 tokens to bid, very expensive
2/ 22 years old average trainer, quality ending in 4/9, good SA for the position, cost 50 tokens, cheaper than (1)
Which one would you buy?
Would your answer change if (1) has SA but not considered useful by you e.g PKS, Dribbler