Assuming there are enough free research labs available.
For every 100pts of research base and 5 labs assigned, the 30%/5 lab generates 650 out of spec, and 1100 in spec. The 20%/20 generates 600pts out of spec, and 900 pts in spec. All you need is to add 2 more labs to the 20%/20 to exceed the output of the 30%/5 researcher.
Of course, the closer the bonus percentages are, the greater the disparity in lab capacity is needed along with sufficient labs to make it worthwhile.
Now, I am unsure of the exact mechanic on which stat gets increased when the researcher gains a bonus, but I've seen a lot more bonus percentage increases than lab capacity increases. To me it make sense to cultivate the high-capacity researchers and improve their bonuses, rather than hoping for a capacity boost.