the Yamaha will be cheaper. they are trying to give those things away now. their stock clutch is still garbage and needs mods to get it past 300 miles before you burn it up. they REALLY need the lower gear ratio trans setup that is available from multiple vendors as well as Yamaha themselves now. They need the gear reduction trans just to be nice and drivable for anything in the woods or trails. Dont buy it if you plan on actually woods racing it or cross country racing it. you wont ever get the suspension to do what you want, and it will never be as fast as the polaris in cross country. short course is a different story because of their wheel base and suspension design, they will take a corner 10mph faster than a polaris. which is why they are destroying everyone in short course. GR transmission, reflash, and in short course they are lethal. but for cross country, they are slow. That pro trophy truck driver that held my lap record for a year, sold his RZR1000 and bought two yamaha machines last year. hes done everything you can do to them, spent days out with fox testing shocks, has had George White try multiple times to get it to his liking and still cant make the suspension do what he wants for cross country. a few months ago at one of the cross country races here, he got beat, by most of the upper A class and by a relative new-comer in the lower B class in a 900RZR. the yamaha is great for some things, racing thru the woods they arent going to put you on the podium.
the maverick in my opinion needs the least amount of stuff to be a race winning machine. S3 powersports Dustin Jones is selling his cross country race maverick. typically he will lap everyone in B class, and sometimes lap all the way up to 5th place in A class. everyone assumed it was the machine was built to the hilt and the other day when he listed it and the list of mods everyone was shocked. its a reflash, intake, exhaust, and clutched 100% stock mav turbo with suspension tweaks and a cage and doors. literally the least amount of mods on a machine that is at the top of the box every race. He raced this last weekend, got jumbled up in the start and at the holeshot a guy with a built up turbo RZR got out front and went into the woods 100 yards ahead of dustin. Dustin went into the woods in 3rd place. towards the end of the first lap, dustin came out of the woods first and it was almost 45 seconds before 2nd place came out behind him. that turbo mav will walk the dog in the corners and trails. it carves, handles, turns, and cuts like that was its sole mission. with minimal mods a mav turbo is tough to beat in any sort of racing.
the RZR1000S is no slouch out of the gate. its stock clutch needs help if you plan to race it, and the suspension and swap bars and shocks need some love too, and you need to beef up a few things, but they are surprisingly quick. they arent as confortable as the maverick nor do they ride as good, nor are they as fast in a straight line. but i am sure they are prob quite a few grand cheaper. to take one of the 1000S and make it hang with the NA maverick in the woods you need to do mods to it. not because its under powered, but just because it still isnt as fast as the maverick. a maverick turbo compounds the gap because they are faster in a straight line and so easy to reflash and get another 20-40hp out of.
personally it depends on you. your budget, and what you expect out of it. if you plan to race any of them you will find things like Tie rods, bolts, motor mounts, hubs, bearings, all these things will fail and you will have to either find upgrades or constantly replace them if you want to race them. if you are looking for a fun trail ride just to sight-see then look towards the defender or general. both have upright seating which will help with your knees and a flat floor like the ranger. you dont have to crawl into them you can just step right in. they are both spunky with a 1000 engine and nearly 100hp. they both have a bed to carry things and both are relatively quick if you want to feel sporty every now and then