It would depend on several factors. I still believe the inverter in the XW-Pro is one of the best on the market. My only gripe is the software issues. They have another new update. I need to load it and see if they have improved things at all. But since all my network is powered off of the backup loads panel, I need to rig up a computer to do the update with my home network down. I still have not installed a manual inverter bypass switch around the XW to power my backed up loads. I have the switch, 60 amp rated 4 pole, but I have not had a chance to tak my system down to install it. I will likely do that at the same time I do the software upgrade.
But all that aside... It truly does depends on the power demands that you need. For my current home demands, I think I would have been better off with the OutBack SkyBox. It is a lighter duty inverter. 5,000 watts compared to 6,800 watts, but that is only half the story. The SkyBox has much lower surge capacity, and also can't handle near as much imbalance between the phases. That is not an issue with my current setup, so here it would work fine, but if I do plan to add a mini split A/C unit off the backup loads, then I will need the grunt of the XW-Pro inverter. It has a 2 minute surge rating of 8,500 watts, and a 30 second surge to 12,000 watts, or 50 amps to get a large motor started. This should easily get your 35 amp well pump going. And since you are DC only, then all of the features of the XW-Pro will work for you. My software issue is mostly due to the AC coupling being my only source of solar power. The XW-Pro handles it great when the grid is down, but the software prevents the system from doing time of use energy shifting when the grid is up with only AC coupled solar. I am still hoping they will eventually fix this issue. The new firmware did add several good features that I am aware of. A big one is having more settings that change how it operates between the grid up and grid down modes. When the grid is up, I have it keeping my battery above 50% charge, and not charging above 85%, while charging at a lazy 25 amps. This is gentle on the batteries, and gives me a good reserve if there is a grid outage overnight. But when the grid goes down, it uses the same numbers. I want it to be able to charge at 100 amps so it will just take everything my solar can produce without having to frequency shift, and top the batteries up to 95% so I have more available to run the next night if the grid is still down. It does allow the inverter to run lower while off grid, and the AC coupling mode works great once the sun comes up. I think they did fix some of this in the new 1.12 firmware.
The other issue of an AC coupled system is what they call "dark start". If the battery does end up running down to where the inverter shuts off, then the system is basically dead. Even when the sun comes back up, it can't start back up on it's own. This is true of all AC coupled systems. With the battery inverter shut down from low battery, there is no local grid. With no local grid, the solar inverters do not have a grid either. They will not start making power. So what happens in my case, I have to use a battery powered laptop, to log into the gateway, and lower the settings for the low battery shut off. So then the inverter will come on again, and it will produce a local grid from the low state of charge battery bank. I have mine set to keep enough in reserve, even on the off grid mode, to be able to run up my backup loads for a while still. Once this local grid is stable for 5 minutes, then the solar inverters should qualify the grid is okay. At that point, they can start making power again. The solar will start powering the loads. If they are not making enough, then the battery will still be supplying the difference and could run down again to the new lower cutoff point. That would be bad, as I would then have to do it all over again, to an even lower cut. But if the sun is making enough, it should exceed the needs of the backup loads, and the excess will then be taken by the XW-Pro to charge the battery bank from the AC coupled solar power again. My backup loads panel average 600 watts and peak to 900 watts, unless we use the microwave. That adds 1,500 watts, but only for a few minutes. My solar can produce up to 3,500 watts. That leave a peak charge rate of 2,600 watts at solar noon. Easily in the capability of the XW to to push, and my batteries to take. That is just over a 50 amp charge rate, my 720 amp hour battery bank won't break a sweat. 600 watts x 24 hours is 14.4 KWHs. My 16 x 300 watt solar panels make more that even in winter here, and I hit 30 KWHs in May. 14,400 / 4,800 = just 3 sun hours to meet my daily backup loads panel demand.
Dark start is not a problem when you have DC solar to charge the batteries. When the sun comes up, there is no qualifying at all. As soon as the solar panels are making enough power to light up the MPPT controller, it will start to push current into the battery bank. On my system, it will only need to raise the battery voltage 0.2 volts, and the inverter can start back up. Then once the inverter is running, the AC solar can even start back up after the 5 minute qualifying of my local grid. For this reason alone, I am looking at adding a few DC coupled solar panels. But after doing the math, I think it will be more like 2,000 to 3,000 watts of DC solar. That will cure my time of use power shifting issue. I use the AC solar when the sun is up, and the DC solar charges the battery, and I use that when the sun goes down. just 10 KWHs of battery charging will cover my 4pm to 9pm peak rate time of use energy needs.
I did look at the Radian setup. I liked the modular design, and the 4,000 watts x 2 setup that would still give 4,000 watts if one of the inverter modules had an issue. But to make it work, it did need a few more external boxes and the spring clip wire terminals kind of scare me for 30 amps of 240 volt AC. It does seem to be a more robust inverter than the skybox, but it's still a bit behind the brute force of the Schneider (Conext) XW inverter. Looking at the manuals and such, the radian does look like a good system, but I have no hands on time with one. The skybox fixed some of my issues with radian, and the software features look great, but the weaker inverter did not seem powerful enough wen I designed my setup, but in hindsight, I think it would be fine for me. And the price of it has dropped a lot since I got my XW, so it is now very cost competitive. With your well pump demand, I think the XW might be the only single inverter that would get that running. My 120 amp Hobart mig welder runs fine off the XW, and it also fires up my "3 HP" air compressor (it has a 25-30 amp start surge, but runs at just 2,000 watts) without complaint.
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