I'm a fan of larger tyres, smallest I have are 700x32, and there are various factors to look at and consider when making your decision:-
frame - these can limit the size of tyres you can run
brakes - these can also limit the size of tyres
speed - lighter, firmer, faster is widely believed and is no doubt true when the rider is able to maximise this potential. It's also perfectly possible to get reasonably light, and fast, wheels/tyres in the 700x28 to 700x40 range. Your own weight and fitness will make a difference as well, heavier and less fit will make a narrower tyre feel harsher. There's the obvious aspect that you weigh more but also you tend not to pedal as much, or as vigorously, thus you sit heavier and differently on a bike than a fit athletic rider would.
road surface - most people seem to accept that larger tyres wil lgive a better ride on a rough surface but there's also a belief that they can give a faster ride as they don't lose as much energy via deflection, or something along those lines.
distance - if you read around you'll see lots of discussion about how a bike/saddle is comfy for X number of miles then becomes progressively worse. There're a lot of factors that can influence this, the first to get right is bike setup, so saddle height, fore/aft position and reach/height of bars. If these aren't right then any bike can potentially give problems over time. But fatigue is a big factor as well, as you tire you pedal less and your posture slumps, this significantly alters the pressure points on the bike. A harsh ride, on skinny hard tyres, can increase the fatigue aspect, how much would depend on base fitness levels.
The problem with taking advice on the net is you don't know the other persons fitness levels, pain/endurance thresholds and experience of differing tyre sizes. For example a lot of people that will say 23mm may not have ridden larger tyres or only in heavy puncture resistant versions. They may also have only experienced alternate rides on very different bikes where bike weight and geometry are a factor as well.
Something I've posted before is a comparison that may be useful, I had two bikes setup fairly similarly, one for commuting and one for the weekend, as follows:-
weekend - carbon/alu mix frame, lightish wheels, 700x23 tyres, 9 speed triple, butterly trekking bars, total bike weight of 22lbs
commuter - steel frame, 9 speed hub gear, 700x35 M+(very heavy) tyres, mudguards, rack, panniers, total bike weight 35bls plus panniers
Speed difference between the two over the same 20 mile route was 1.5-2mph, at my speeds that equated to a time difference of 5-10 minutes. I would say that the fatigue levels were pretty similar.
A lighter bike with skinnier wheels will feel much faster than it actually is in reality, the time differences are enough to really matter if you're competing.
Glad no offence taken. 
