Portal axles give you gear reduction and ground clearance.
When you lift a truck with solid axles (like a RAM 2500) you raise the body and chassis and some of the drive train (i.e. the transmission and transfer case), but you don't do anything to raise the lowest point on your vehicle - the differential housing in the axle (a.k.a. the pumpkin). You still drag the differential over rocks, your axle tubes get hung up, etc.
When you lift a truck with independent front suspension (like a RAM 1500) or fully independent suspension (like a Hummer H1) you actually do raise the differential of the independent axle(s), but then you create problems with your drive line angles - as photoed above with the RZR's. Trucks are not very tolerant to out of OEM spec drive line angles and to compensate for this many independent axle lift kits will actually use drop brackets to lower the differential section down to maintain drive line angle; so now you are back to not gaining any meaningful ground clearance for the lowest part of the vehicle - the differential.
Here is a great shot of an IFS differential drop bracket - see the metal plate with "RCX" cut out? That's part of the bracketry that lowers the front differential to try and maintain the factory drive line angles:
Now - portal axles replace your factory axle hubs with a "portal box" which has gears inside of it. The top one is where your factory axle goes and the lower gear is where your hub goes (where your tire bolts on) - see the photo below.
So by putting this "lift" on the outside of the axles you actually lift the entire axle, differential and all, and you maintain the factory drive line angles. Portal boxes also allow you to have different reduction ratios so you can get SUPER deep crawl ratios (like a Unimog) and, as was said earlier in the thread, actually reduce stress on upstream drive line component (e.g. axles, transfer case, etc.).
So - do you need portal axles? Based on how you described your use case, absolutely not. You're looking at 10's of thousands for a kit (if they even exist for RAM) or you're going DIY. You need to deal with ABS, traction control, all the other computer crap that the RAM has on it. It's not worth it IMO. You'd be better off buying a more capable off road rig that has portals from the factory, or something like a Jeep that has a massive aftermarket available (which have bolt on portal options).