I think a 1.8 turbo addict!!!!!
That Allard one is huge!!!!!!
The AM one looks quite small????? Laguna and Forge looks bigger?????
Depth of core also... AM one is thicker than a Forge one for example.
Count the bends and pipe sizes between em also, tightness of bends, construction of bends, rows of the cores, internal construction of the IC itself... vbar & plate or vacuum brazed extruded, internal turbulators etc etc etc - Its all a factor on how well the end product works. Not just how big is it.
Think of a small thin core but large surface area.... great for big surface area to heat exchange, but not so good for flow & pumping losses to push through a smaller core.. Think larger single pass core but not many rows, and how long the dwell time is within the core to actually heat exchange.... think about airflow distribution through the core to make use of the available surface area for heat exchange evenly.
Been thru all of the aspects in the various versions and revisions I have had personally. AM's fabricator with direct input created what seems to work fine for me when 320bhp and now 485bhp. Its is big, it needs chopping to fit, its not the cheapest of the bunch (probably), but it suits my needs.