I went for 1100 path myself, in terms of "cheap and cheerful" as they say here.

I always consider a possibility the bike getting crashed/totalled or stolen. You can be almost certain you get no money back if someone totals your bike (not with your fault) in third world, insurance simply doesn't work there in most cases. I'm a poor bastid myself and thus don't want to lose an expensive 1150 or even more expensive 1200 I'm maybe being a bit too paranoid here tho., but this is the thing always to consider if your wallet isn't exacly a thick one. 1150 and 1200 look modern by outer design, while 1100 looks like from a previous century, so doesn't get any real attention from those eyes who may have a potential to steal it from you. If you got loads o' dosh to replace any bike any time, then things are different of course.

1100 and 1150 are exacly the same in terms on maintenance. Technically very similar to each other, also in performance. Dead easy to work on it your own, they're robust. Replace oils (engine, gearbox and bevel box), air filter and valve check/adjust etc routine works. My 1100s have been chepest running costs bikes I've had.

What I don't like about 1150 myself is the extremely tall first gear making it a bit bulkyer to offroad and more usage of clutch. Also 1150 is 6 kilos heavier than 1100 with the same configuration, ADV even more. If going 1150 I'd take ADV version with shorter 1st gear, pro for ADV is longer suspension travel, which is good if you're a skilled offroad rider. Tho 1150 ADV was much out of my low budget.

ABS was one of my requirements. More simple and proven ABSII (non-servo) that 1100 and early-1150s had was a pro, since there were some servo-assised ABS (later 1150) problems reported that made me a bit worry, altough this could be also my own paranoia (this ABS problem could be as well as "a tar drop in honey pot" phenomena and BMW says they have a solution for it). If ABSII fails somehow, it just disconnects itself and brakes work as normal brakes on a non-ABS bike.

If aiming 1100 I'd strongly recommend later 1997-1999 models. They are ironed-out ones, pre-1997 had some issues (mainly "lottery to failure" gearbox was the major one that kept me away from them).

1200 was a way out of my budget and although most of the issues are starting to be ironed out but you then need to buy almost new or a brand new one (£££). I've testridden 1200 and it's a superb bike, although the weight difference isn't that big as people say when you compare them through a comparison test ride, on tar there's almost no difference, on offroad you feel some difference, but not that big. Seat for me and especially for pillion is more comfty on older 11xx models. Performance is much better on 1200, more than I'd ever need tho. 1200, unfortunately, is out of my budget.

All of them boxers are good mile eaters and capable bikes, especially for cold and wet weathers we have here in Northern Europe - roomy, heated grips as standard, cylinders keep your feet warm and dry if you put additional flaps (I made them myself for example) you feel like home , just take the flaps off if going into a warm country. 1100 and 1150 have more boxer "character" apparent than the 1200 with balancing shafts, riding my 1100 always makes me grin, altough on 1200 you often grin thanks to it's huge torque. So any of them is an ideal bike for me if doing long travels, solo or 2up, using it everyday communiting and they're surprisingly capable and fun offroad too if you're not afraid to take a big trailie offroad. For me they represent a rare combination character and capability.

RS/RT are road-oriented bikes, engines are very similar to the GS cousins, just few more BHPs for road use and also maintenance intervals usually are almost identical. If riding on bad roads and offroad you need to aim for a big trailie.

650GS is very nice bike if you ride solo, I've ridden it for some longer distances: sufficient comfort and performance for solo but for my 2-up needs it is too small, both in terms of space/comfort for me and pillon and performance. Altough some can travel 2-up with a 125cc too...

So in the end, it depends from the rider, his/her needs and budget, as always... This was my, fully personal version. I'm sure some may not agree with my 1100/1150/1200 comparison.

Hope this helps, Margus