We've changed from SS to Excel Sensitive - has a higher fibre count than Excel, but they love it just as much.
We only changed from Excel because of the amount of times someone told me they should be on SS, but Tibbsy has "choked" on it three times, and I'm just not comfortable with that.
She is very greedy, and gobbles her food - the Excel Sensitive seems to need more chewing so it slows her down.
We're delighted with the change - it is slightly more expensive as it only comes in small bags, but we've found a cheaper supply, and are spending less on hay so I'm not too bothered.