Dewitts, a US MFGR of Radiators, very well known in the Corvette community, has a great blog post that explains the importance of total tube-to-fin area to radiator performance and that sometimes, when you have really wide individual tubes, a 2 core radiator can cool better than a 3 core radiator or a 3 core vs. a 4 core and you really need to take the time to evaluate the total tube-to-fin area:
https://www.dewitts.com/blogs/news/14141757-are-three-row-aluminum-radiators-better-than-two
Some cheaper imported radiator cores are made with only .062" wide tubes, but .075", .100", and even .125" wide tubes exist and the wider tubes will expose more area to the cooling airflow and cool better.
Ultimately Tom Dewitt recommends taking the tube width x the # of rows to determine the total tube-to-fin area.
A few real examples for some C3 Corvette radiators:
Dewitts:
Pro Series for 77-82 Corvettes: 1" wide tubes x 2 rows =
2" tube-to-fin area
HP Series (highest perf) for 77-82 Corvettes: 1.25" wide tubes x 2 rows =
2.5" tube-to-fin area
I'm sure many of the ultra cheap imported cores have the .062" wide tubes, but below I'm looking at two of the more popular and good rated off-shore radiators for comparison; you only get into the thinner tube widths when moving to the 4 row radiator
Champion:
2 Row: .75" wide tubes x 2 rows =
1.5" tube-to-fin area
3 Row: .75" wide tubes x 3 rows =
2.25" tube-to-fin area .25" more than the Dewitts Pro series for $245
4 Row: .63" wide tubes x 4 rows =
2.52" tube-to-fin area .02" more than the Dewitts HP series -$295
-The Champions do NOT work unmodified stock rad cushions and require trimming them to the right size and profile; NOT a direct fit.
Cold Case:
CHV718A: 2 Rows with the same 1.25" wide tubes x 2 rows as the Dewitts HP series and corrugated fins @ 16 fins per inch like the Dewitt. =
2.5" tube-to-fin area.($417.55 vs the $990 for the Dewitts HP series)
-These are reported has being direct fit and working with stock-style cushions. (Assuming you're replacing a stock 3" thick radiator)
These Cold Case radiators seem to be just fantastic amounts of cooling for the price. I wish I knew more of this stuff back when I purchased my Champion 3 Row, but for the money I'm still happy with the Champion; but if I could go back in time I'd pay more for the Cold Case.
I'm posting some real-world examples, but I think paying attention to the tube-to-fin area and whether the fins are flat or corrugated can help make pretty informed decisions on what the radiator performance will be like AND to identify cost-savings opportunities.
-I think there's some improvements that have been made to copper radiators over the years that are worth talking about at some point later, too...
Adam