Kathleen B,
When our pumps are returned we clean each one and at the same time test the
suction pressure with a pressure gauge.  We find that we get substantially more
suction with the Classic pump.  Also, we often get specific requests for one or
the other.  I can remember being out of Classics a time or two and losing the
rental to someone else who had them.  I know the Classic is costing us more,
but for our rental station they are a must.
Yaffa