Given the same area of fins and capacity of tubes the difference is neglible. What will make a difference is the style of fins.

What makes a HUGE difference and why I'd never get another downflow if I had the choice is that the downflow tubes will plug up a whole lot sooner than a crossflow will. The crossflow will lose one or two tubes at a time. The downflow is losing whole areas where sludge is gathering.

My 6 year old Dodge Durango lost major cooling ability last summer. If you put your hand on the rad. fins it was obvious that several sections of tubes were cooler and limited. In the span of owning at least 3 crossflow style rads in off brand cars.....I've NEVER had to replace a radiator due to blockage in 20+ years.