Hi mate,

Happy New Year! Welcome to the forum.
Couple of things from me to answer your questions:
if you will be using the bike predominantly on-road and as you say "for fun" then get the x, you will love it
if you plan some green laning or moderate off roading get the R
the Z is as good bike where the main advantage is the big tank but if you do not plan round the world trip you will not need it as it is around 20 kgs heavier than the R
regarding reliability and milage - do not worry, no reliabilty problems and the engine should last at leat 60-70 k miles
hope this helps.
Enjoy it is great fun.

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that is how i feel about my XTR
Mods so far:
Hyperpro front springs; Hyperpro rear shock spring; modified air box; LED tail light; LED indicators + new relay; YZ pegs; Lucas aluminum bar; brisk spark plug; snorkel removed; DNA stage 1; second hand DynoJet O2 mod; crash bars; front and rear steel braided brake lines; soft EBC brake pads; mitas 07 tyres, 2in1 Metal Mule exhaust, Blocked AIS, tall OEM screen, OTR bash plate