Pretty similar. It depends on your preference on a few points.
Durability- Yes, glass is more breakable than metal, but most glass toys are made of tempered glass and are very very hard to break, so this should be a marginal concern at best. And metal, if not treated properly, can rust.
Weight- In most cases metal toys will be heavier than glass toys.
Appearance- Glass toys in general are colorful, while metal is simple and shiney. Each material can take a number of shapes and sizes, and most often they could be mistaken for art if left out on a table. With glass you can find your favorite color or combination of colors... unless of course your favorite color is glossy silver. Then go with metal.
Texture- In general, glass toys offer more texture options than metal. You don't see many texture options with metal, but there is the njoy eleven (if you can take it)