Dr. M said:
JA -
enanthate has a linear, 7-carbon chain; cypionate has a 7-carbon chain which has a 5-membered ring on the distal end.
Think of it this way in terms of structure - enanthate is like a pencil, and cypionate is like breaking the pencil in half and stabbing it into a tennis ball.
Bad analogy, but I guess you guys probably get the idea...
-M