All coaches handle different and all drivers are different. I have made the trip from Florida to California several times in my Monaco gas coach, mostly during the Winter when the winds are higher in the Great Plains area of the country.
As suggested it is tough to state which will be better without knowing all of the facts. Perhaps your current coach has some suspension/alignment problems that make it more difficult to handle on the highway. Naturally buying any used coach, DP or gas, may also have suspension/alignment issues that will cause the same problems for you on the highway.
It could also be that after 1000 miles you have not yet adjusted to driving a large RV and switching to another large RV may not be an improvement. I can't really say how long it takes to get comfortable driving a large RV on the highway with varying weather conditions. It all depends on your abilities and your own expectations.
On one of the forums where I belong, a couple put their brand new Monaco coach up for sale. They picked it up at the factory and by the time they got back to Florida, they were so afraid of driving it that they immediately sold it and took a huge loss. There was nothing wrong with the RV and the new owner was thrilled at the bargain he got.
Perhaps your first thing you should do would be to have a well experienced person take your RV for a drive on the highway and get his opinion of how it handles. This might give you a place to start as to determining whether the problem is with your own inexperience or if there is an actual problem with your current coach. It might be a simple issue with the wrong tire inflation pressure or an alignment. Buying any used coach may or may not be an improvement in the driveability of the RV, especially if the next coach also has suspension/alignment/tire pressure issues. Identify the exact problem first before throwing any more money at a perceived fix.