I like this game as an insect genocide game (the "War of the worlds" interpretation of Hectors and other Ravager machines is particularly powerful) , but I really hate the grinding and I wish they had done that differently.
The thing about it, is that appears to be a solution to a problem that comes specifically with online coop: how to distribute 'powerups' and get people to cooperate instead of getting turned off and dropping out.
In EDF3 (2017), coop is always local and resources are pooled. Cooperation arises naturally in this context, because everything that either player does benefits both at the same time. Since this also negates the need for any kind of scorekeeping, aside from the amount of enemies left, there are no distractions from the actual job. Working for the same cause and with a wide variety of weaponry (and limited aggro on enemies), means that within moments of starting to play, you'll find yourselfs discussing strategy and options.
Having short levels (which are more like scenes than levels) also allows for quick trail & error, without losing a lot of powerups and getting frustrated.
In IA, both powerups of weapons and armor are locked down to your rank (even those you pick up in missions) and all coop partners have an individual ranking. Meaning that despite being coop, it's still very much every man for himself when it comes to your advancement in rank. The wierd thing about it is that the score in each mission you play tends to divided over three people anyway. I can think of some reasons why that would be, but the most likely one to me seems 'Call of Duty syndrome' where nobody gives a fuck what anyone else ("team, lol") is doing. Obviously, when the aim is to prevent random people from dropping from a game (which may also deny partners their advancement), this is a good thing to have if that means people will actually stick around. It may also be that XBL and PSN allow little other means of keeping track of advancement, as they need to be tied to a specific XBL or PSN account.
The obvious downside however, are the long levels that are needed to give people ample time to play together anyway. There is nothing more frustrating than building up a high score, spending tens of minutes on a missions and then have everyone killed off quickly in a later part, with nothing to show for it in terms of advancement / powerups. One level in particular would benefit immensly from being a two-stage or checkpoint enabled level instead of everything in one go.
Tying all powerups to rank just reinforces that frustration, as you cannot farm armor indepently and retry after that. If you get stuck somewhere, your only option is to go back and do some really dull, repetitive farming. Yet in EDF 2017, where armor is separate, you can farm, retry and farm some more if you still failed, but you're going to succeed at some point anyway.
All of this combined makes grinding in IA to be a rather dull and unrewarding process, where the Sandlot version avoid that problem.
If EDF 4 is going to have online coop, I hope powerups will be party based (every collected powerup counts for everyone in the party) and that the mission selection will be as well.
I doubt that Sandlot has those kinds of funds though.
Regardless, I'll be more than happy to keep playing offline.