RE:Simms breathable waders
I prefer the stockingfoot waders because I like the comfort when walking long distances. Although the bootfoots score big points in convenience, they fall short IMO on ankle support. I like the more secure feeling of the boots, as my ankle doesn't feel like it is swimming like in the bootfoot models. Probably the best compromise is the breathable waders by orvis, combining the convenience of the bootfoot with the superior support of the separate boot -- Sounds a little like ad copy - sorry.
I have done a lot of wading in rivers with extremely slick substrate, and feel the separate boots have saved me a few falls. I just seem to be less clumsy in the stockingfoots, plus I think the tighter fit around the ankle allows me a more positive foot plant. If this sounds whacked out I understand, but when you prevent yourself from dunking with a fancy pirouette and some fancy footwork you'll appreciate the stockingfoots.
One thing to consider is winter wading - when temps get real cold you may not want stockingfoots as you may have to cut the laces off to get them off, or defrost them in your car/truck before removing them - then the boots come in handy.
One more thing - I can adjust the amount of foot insulation I use with the stockingfoots. In warm water I wear a thin atletic or wool sock and when colder conditions warrant I step up to a heavier sock and polypro wicking layer - affording me more flexibility and comfort level. If wet wading I can just wear the boots, and take advantage of the traction of the felt bottoms. Also, like Juro mentioned, some of those bootfoots are dark in color - the suns rays combined with some insulation equate to some hot feet.