As others have said - it depends...
Had National General for 2 years with this RV... They rewarded my 2 years of on time payments, no change of address (at that point), and no claims or tickets with a 20% increase in the next renewal...
Now with SafeCo for the RV.
Both were direct with the company - not through Good Sams or FMCA.
While there can be benefit to one provider for all insurance needs - haven't been able to do that since getting the RV...
State Farm was my home/auto/liability provider in Michigan, but was absolutely not competitive with RV terms and rates (they admitted wasn't their specialty)..
Moving to Florida (never seen a state with such convoluted insurance - I thought Michigan was bad...) - I now have 5 different insurance companies... will need to consolidate that somehow - but its ugly.
USAA has my cars from when I moved here initially - but wasn't competitive on the RV (they use Progressive for RV policies) - so that remained with SafeCo. When we bought the house USAA wouldn't write a policy in this zip code... Citizens covers the house - but doesn't offer liability limits that meet the umbrella requirements... Gap insurance for that through another company (only one company seems to offer this)... And the umbrella had to go thru yet another company since others wouldn't cover the spread out policies.
Now trying out (unfortunately) USAA's claim handling for a comprehensive claim... We'll see how that goes...