I've only got a lowly 1204, but I'll throw in my .02¢... I don't know how big of an issue speed is for you. If speed is king, go with the 1618 as it is rated for 480 sq ft/hr vs 313 sq ft/hr for the 1624.
But if it were me I'd go for the 1624, here's why;
- Overall improved machine with...