toto supreme

I had a hell of a time getting the flapper off the flush valve on a one-piece Toto CST864 toilet -- and ended up breaking off one of the pegs that holds the flapper on. Now I need to replace the whole flush valve, only to find that the tube is now replaced with a tower. Is this a relatively easy...

We need a low profile toilet and was recommended a Toto Supreme ii. I found a Supreme on for $150 less than the Supreme ii. What am I giving up? Is the ii worth the extra money? Also, any other low profile toilets I should be looking at? 24" or so height is good. Thanks!