If it was me, then:
1. I wouldn't buy the 1995 one if planning to do a lot of mileage and keeping it for a long time! Reason - gearbox could fail relatively soon. The 95-96 models have noise surpressing bearings in the transmission that was a mistake by Getrag (the company making gearboxes for the BMW). It makes less noise, but it's prone to brake down on higher mileage. Usually i've heard at constant 60-90Kkms. Starting to kick out 3rd etc. Read
here
2. Earlyer than '97 have non-anodized wheels - more pain in the arse cleaning them and have to use special chemicals to avoid rusting.
3. Rear frame is reinforced better on post '97 - better extreme offroad or riding with excessive loads on bad roads. Altough i highly recommend to get Touratech HardPart rear frame reinforcment kit on any 1100 you'd get, just to be sure, they don't cost much indeed (less than 100EURos).
Not to worrie about the mileage - the engines are good easily for 300,000+km before top end overhaul on all 11xxGSes. BMW original consume bits are cheap and it's very cheap to keep them on the road for daily communiting and travel, they also have long maintenance intervals, every 10-20K. I consider fuel consumption very low for a 1100cc bike with almost no fairing orher than a small windscreen - i get around 4.5 to 5.5L per 100km average, depending on my right hand's action.
So if going for 1100 - i'd look for '97-'99 models only, they are one of the highest reliability standard on the whole GS line. Or if earlyer model with very attractive price (well it really has to be an attractive price! Getting the new M97 spec gearbox for older and cheaper will take a lot more $$$ than just to buy a post '97 1100 bike at the first place) check if the BMW has done the gearbox mod (the M97 gearbox), some of them had them repaired by Getrag because they understood their mistake and was replaced under guarantee, but usually the "braking-down" symptoms started to appear on higher mileage 60K+, so not much older bikes got the M97 gearbox mod, due they didn't reach that much mileage before they were considered "old". The first 1994 version gearbox is acctually better than the 95-96 when the noise surpressing was used, but the '94 bike has it's own "teenager" problems, it was the first oilhead GS, mind. '97-'99 are the most ironed out ones.
But if you don't plan to do a lot of miles and long travels, then from this perspective the older 1100 are as good as newer ones imo.
For more "newbie info", it's a
good reading here.
I've done more than 60Ks on my '98 1100 in two short riding seasons we have here in north, doing every day communiting to very long travels and I only can highly recommend one.
Hope this helps.
Happy travels, Margus