30% is just 1'5 stars, is like a 3'5* vs a 5* so is a advantadge but not the differance. You can equalize doing lke I do, vs 9* I face them having phisicall skills at same level, so sped at 180% min. (now in then new version we have to count that theres no limit of +20 of quality as max differance between the min group of skills and the max. so maybe 200% would be better to have options t face 9* teams ) and then the bonuses, in training and $, and good selection of players that should work.
Believe me, is not da differance 1'5*.