Basically you want the most flow with the smallest ports you can get. If you have two heads that both flow 300 cfm...but one is a 200 cc port and one is a 230 cc port. Tha smaller port should make more power throughout the rpm range.
But to say smaller is better in general is somewhat misleading. It all depends on the apllication, target rpm range etc etc.
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if it's cheap & reliable, it ain't fast, if it's fast & cheap, it ain't reliable, if it's fast & reliable, it ain't cheap
