I have no way to know what would be "worth it" to you with your camping situation. The more you learn about battery charging, the more you will appreciate having the adjustable charger.
Also I cannot advise between he 75 and the 100 amp models for your size battery bank, your generator size, and how long you are willing to run the generator at a time or else what the gen hours limit is in your campground.
If you have a Honda 2000 you could run the 75 amper with its PF correction, but not the 100 amper. If you have two batteries at about 220AH total, the 75 adjustable set to 14.8v will be perfect for a fast charge. If you have four batteries at about 440AH the 100 amper would be good, but needs the Honda 3000. But the 75 on a 2000 will still work on four batts, just takes a bit longer to do a 50-90.
IMO assume you will learn more about all this as time goes by and get the adjustable voltage one now so you won't have regrets later. :)
this is good reading--helped me figure it out.
http://www.bestconverter.com/Books_c_67.html