The Device Rating of a Deck should only matter for the size of the PAN, so 3 more devices in the Deckers PAN is nice but really not worth much cost as you'll likely still have to get a separate Commlink if you're handling the team's gear for them.
Program slots. Two Program carriers and Virtual Machine means even the lowest end Cyberdeck can be running four programs.
Matrix Attributes are, obviously, the big seller here so it kinda depends on your dice pools and the rest of your build. Can you with swaps/programs/mods/qualities/whatever get your Matrix limits up to half your best dice pool for the important tests? If not, then possibly you'll want to look at the better deck. Example Erika MCD-1 best Attribute 4, Overclocker, plus relevant program drags you to 6 for any non-sleaze test. (Sleaze tests with Smoke and Mirrors running shoot up to 10 Sleaze, so no worries there). Do you commonly throw more than 12 dice at any Attack or Data Processing test? Probably. Do you care? Maybe. 6 Hits on most Data tests is usually fine (ish). Cyber Combat against Hosts will get problematic as half your rolls will likely be at or over the Decks attack limit.
This is where the rest of your build starts to matter. Are you a 7 Edge human Decker? Then phishaw. Erika MCD is fine, just be smart about when you blow the limit. Are you an Orc Hacker with 1 Edge? Then you'll likely need to get at least the Azteca 200 or Little Hornet so you can drag the Limit up by one, and honestly the Novatech starts to look like a wise choice if you've got some good pools in Matrix Perception or Cybercombat that you don't want to waste.
Deckers and upgrading decks... honestly unless the GM hands one out as phat lewt you're better off raising your Edge. Going from 1 Edge to 6 costs 100 Karma, or about 200,000 Nuyen. At best one of the mid-range decks. And if 6 Edge isn't enough to get you through a run, you're doing something wrong.
I also gotta think the Increase Limit Spell could be quickened on your Deck for less than 200k.