In terms of policy application, there should be no difference between an MX and an MR, however as mentioned by @ww, you will get to restrict the traffic going to/coming from certain countries when you have adv sec license.
I would still prefer to have an MX to do all the cool stuff like content filtering, AMP/IDS to keep you more secure which a router can't do but if you are only looking for layer 7 policy application, then yes, you will do just fine with an MR and a router.
Cheers!
Raj
If you found this post helpful, please give it kudos. If my answer solved your problem, click "accept as solution" so that others can benefit from it