Just noticed that you had attentioned this query to me, my apologies that I never responded to you on this.
I think that you would have gone ahead with the procurement of the checkweigher by now.
Well, Garvens are part of Mettler, so you are essentially comparing the products of a single company only.
Mettler do provide reliable high speed check-weighers for cans and I think that their highest speed check-weigher can do upto 700 CPM for 400-500 grams cans. So, they may be the right choice for you if you are looking for high speed solution.
The solutions suggested by Automan and Ferrera may also work. If you haven't decided anything as yet, you may explore those options as well.
Well, you are the best person in terms of comparing various products basis the criteria that is important to you, but as you may know, you can compare the technical features of various machines by selecting the machine category and subcategory from the widget on top of this page.
All the very best and let me know if I can be of any help.