Great feedback from everyone thus far; I would add that if you have the Sage 14' brownie the Expert is tighter, if you have the 14 Euro, then yet it flexes more fully.
But listening to your actual question, you were looking for something a little lighter. My honest opinion is that the Expert 13' 8wt (1308) is one of the easiest casting rods I've ever handled. Try it with a mid-length line like the 7/8 midspey, and then put the 15' type 8 tip on the Windcutter 7/8/9 - you should get booming casts without working hard.
IMHO you don't want a stiff spey rod. A stiff speyrod requires that the arms do the loop creation verses the kinetic energy in the rod flex. A rod that flexes does the work for the caster. IMHO a spey rod should flex fully but not be soft, such that the bend in the rod transfers into high line speed. I also find that as you go through the gamut of cast variations (singles, doubles, snaps, snakes, pokes, etc) the rod that combines smooth loading, ability to carry that load thru, and release it with vigor is the nicest to cast all day. Both the Loop Yellow and the Expert are easy casting rods. You can't go wrong either way.
The Customs add a higher modulus graphite to the equation (IM7), the Specialists higher still (IM8). All CND rods will flex, but as the modulus increases the speed of recovery and overall power increases. Yet the Expert should not be considered any less of a rod, it's a mature time-tested design that is the favorite of many very capable casters. I'd describe it's action as "su-weet". The way I see it, CND headquarters decided it could be offered at a lower price point to round out the product line so the consumer wins.