As an engineer (civil/structural not electronic/electrical) - 3 points of support is ALWAYS preferable to 4.
Reason: This is known as Hambly's Paradox. Ask (most) people which is stronger - 3 or 4 legs on a table, they'll nearly always say 4 legs. Logically all the weight (mass) distributed four-ways rather than 3 means that less strength is required in each of the legs which has got to be better?
Uh - not always. If you put your table (or CD player) on a surface that is not entirely level it will rock. At some point two of the legs will be up in the air as the table rocks back and forth, at which point it is supported only by the other 2 legs on the ground. So the weight whichwas designed to bedistributed through 4 points of support (legs) is now only distributed through 2 points of support, effectively increasing the load by 100%.
If you only have three points of support, this CANNOT happen, the load is always distributed by the three points (but not necessarily equally obv.), and therefore determinable, and therefore can be designed. Anything less than 3 points of support obviously means the thing falls down.
If the three points of support are correctly designed, they will always be more stable. The clever bit is in the design of those three legs.
Camera tripods? Theodolites? Surveying levels?
Of course this is not the same as being level! Having set up a fair few levels and theodolites in my time, I can confirm why thy have three levelling screws and not four!
Sorry to get all logical on your ass, but them's the physical facts!
(waits to get shot down in flamessssssssss)