a few points to consider if you will

generally speaking the faster the flow rate the better the ΔT's. the medium's total residency time in either the I/C or H/E remains the same over long periods of time, just in shorter periods.

assuming proper flow rate and H/E, a single pass I/C will most assuredly perform better. the best heat absorption occurs with the highest ΔT's and a triple pass can actually degrade the performance. how much better a single pass performs is a vaild question, but it will be better.

another factor in heat absorption of the medium are any additives beyond normal distilled water. Anti-freeze has a poor heat coefficient roughly 1/3 of water i believe. the higher the heat coefficient the higher the heat absorption it can achieve.

laminar flow is a bane to heat absorption. optimum heat transfer is achieved with water impingement on the target areas. question is how to achieve this in a unit like an I/C. i have no answer for that one.

anyways, my thoughts.