I've kept both loaches and Cory's for years in the same tank too.
There's loaches and loaches; and even in the genus "Botia"; there's a wide range in behaviour!
And of course, some Cory's are fragile, while most are fairly though, as small catfishes go.
For really up-to-date loaches info:
http://www.loaches.com
And as far as snail-eaters:
The best two snaildestroyers are
-Botia macracantha (Clownloach): the two drawbacks of this species are it's EXTREMELY sensitivity to white spot (itch, ick or ichthyophtirius) and its' sheer size; adults can reach a foot in length, given enough space. It IS however THE most colorful loach, and very social and peaceful.
-Botia sidthimunki (Dwarfloach): this is an endangered species in the wild; fortunately there are more and more captive breds available. Like the Clown, it's highly social, diurnal and sensitive to white spot. Most varieties grow to 5 cm or so, but a recent batch of Thai-sidthi's are bigger than 10 cm....
These two Botia's even eradicate the Malaysian Burrowing Snail.
Other good snaileaters, with peaceful and social behaviour are B dario (Queen Loach), B striata (Zebra loach), B rostrata (syn B geto), B almorhae (syn B lohachata, the Yo-Yo Loach), and Botia eos (Sun loach). They can be a bit picky, and sometimes don't want to eat the Burrowing snail. Other snails are toast, however!
Botia morleti (syn B horae), the Skunk-botia is also good at snailcontrol; this one however, has been known to get aggressive sometimes, and if you have a 'bad' one, it's able to kill co-inhabitants. For Botia modesta (Orange finned Loach) it's the same, although usually it's more peaceful.
The bigger longsnouted Botia's, like Botia hymenophysa (Tigerloach) should be avoided: the Tiger is as good as its' namesake, and pound for pound one of the nastiest fish in Asia. It gets fairly big too. Excelent snailkiller, but usually kills more than just snails....
ALL peaceful Loaches are socia and should be kept in small groups; for the Dwarf it's even better to keep a true shoal (>7 fish).
Other loaches can be fun to keep, but they rarely eat snails; the Cobitis, Nemacheilus, Noemacheilus, Pangio (Kuhli-loaches) and Acanthopsis (Horsehead loach) loaches are pretty, peaceful fish;usually, but they won't kill snails.