I'm not disagreeing with you at all. You're right, the same company doing the evaluation should have the same dollar figure, except there are reasons why they wouldn't. I'm guessing their "comparables" are based on different criteria or another bike sold between evaluations. One of the evaluations is probably based on different distance from your zip or something like that. I know I would argue to open a wider market if I thought our insured's vehicle wasn't very well represented. Say a valuation was based on comparables within 150 miles from your zip code, if the values that came back seemed low, I'd argue that we should increase the radius to 300 miles in hopes it included vehicles that sold a little higher. It might be reasonable, and it might hold up in court to use 150 miles, but if I could justify a higher comparable value for my insured I would. Sounds like your insurance company is trying to help you out as much as they can. They probably don't have to, and the other person's insurance is probably doing everything right (just not going out of their way to help you). I could be wrong, but that's my take on two different values.
Or, the other person's insurance doesn't have all of the information. Maybe they don't have all the farkle information, or have the mileage wrong, OR, and this could certainly account for it, maybe they are valuing your bike in the condition it was and your insurance carrier is adding $1000 for gear and accessories.
On a lot of policies there is a $1000 extra coverage for accessories. Accessories very seldom add much value. A $1k worth of farkles might add $150 value to the bike. Not because your farkles aren't worth it, but the value is based on what Average-Joe would pay extra to have those farkles. A lot of times the farkles are owner specific (i.e., having $1k worth of suspension upgrades may mean very little to the guy looking for his first bike, or you're 150 lbs and I'm 200 lbs so I have to get it re-sprung anyway). Sometimes an upgrade adds no value at all. A HID headlight wouldn't add value to a bike for me because I don't need one, as an example, so two bikes exactly the same except for that...well, I'd buy the less expensive one. Anyway, what I'm getting at is farkles mean very little in the determination of actual cash value; however, your policy may have an extra coverage for accessories that is driving up the value through your own carrier that wouldn't be dollar-for-dollar through the other carrier.
Another aspect is "actual cash" value (ACV). What's the cost of a bike if you walk up with cash. Usually it drives the price down a bit. So, the insurance company doesn't care about financing, percentage rates, terms or anything else when they determine a value. When I had to research my own values I'd literally call an owner with a bike for sale and tell them my insured (or claimant) was getting a check that they could cash and could bring $100 bills. What's the price of the bike if the guy brings you $100 bills, pays cash. It always was less than the advertised price. That drives down the "actual cash" value.
So, there are reasons why there might be a difference. If they used the same criteria though, there shouldn't (unless there was some outlier bike that drove the price up or down, which happens). What you can do though is ask for the valuations. In my state we had to provide them and we would readily, because ultimately an informed person is easier to settle with than one that is arguing based on emotion. I hope that helps explain.