I don't know much about Juniper but I'm about to learn with a new job. If I'm going to take full routes from a couple of upstreams and have a couple of peers will the M10i (768M max) be enough or is the M20 (2048M max) a better choice. Layout here is such that I'd expect to use a single quad gigabit port ethernet blade in each of a pair of M10i/M20 to achieve redundancy. The M10i is perfectly capable of handling the full table and then some. The only question is whether you want to buy more just in case your needs grow.
That said- Last time I spoke to a Juniper rep I was told that their 4 port GigE card for the M7/M10 is oversubscribed 4:1- ie the backplane connection is only gigabit. Check into that if it is important to you. I may have been misled or things may have changed- frankly I didn't look into it much as an equivalent Cisco solution with additional ports came in at 1/4 of the price :(
Is there a pricing resource for this stuff online some where? I do *not* want to hear from any sales people over this comment ... The pricing for all of this stuff is so ludicrously flexible it isn't funny. If the company wants you as a client (for marketing reasons or whatever) then suddenly a $50k router becomes a $25k (or less) router. If you point out a competitors router is xyz dollars less you may suddenly find yourself with yet another discount. Get quotes from everyone, compare features, and don't hesitate to push for better pricing from everyone.
-Don