I use plastic plants and they look great:D.
The ones I use come with weighted bottoms, but some plants use a hollow bottom so you can fill it with sand to weight it down.
My turtle never ate any of my plastic plants. I've seen him take a bite once, but stopped ever since.
I've heard bad things about silk plants like algae growing on it, but I've never used one personally.
Here's a suction cup plant:
http://www.thatpetplace.com/pet/group/9565/product.webThey're not too common.
As for which is better? You can try a local pet store to see them in use. They should have aquarium displays.
Lastly for gluing there's aquarium safe silicone, but i don't know specifics or how to use it.