I've not posted on this forum since selling my ST1100 back in 2013, but having just spent a few weeks riding a ST1300 I thought I'd leave a few comments in this thread.
Keep in mind my ST11 was sold over 4 years ago, so comments relating to that bike are from my rapidly malfunctioning memory....
Looks - ST1300
In my subjective opinion, the 13 is a much better looking bike than the 11. Both are old designs now, but the 13 to me still looks OK. I never liked the look of the 11, always found it a boring design. The dash on the 13 is more my taste than the ancient 11.
Comfort - ST1100
I found my 11 very comfortable and I could easily ride 400kms (a full tank) in comfort. I can't remember what screen I had but it worked really well and provided a nice quiet air bubble.
I didn't get on so well with the 13. The electric screen is a good touch but was really noisy in all but the highest setting, when I still needed to duck down a bit and look through the top of the screen to be at a reasonable wind noise level. The seat and peg position I found cramped and not comfortable after about an hour, and I found the 13's seat to be pretty uncomfortable in itself.
I also found the 13 to be like riding with a nuclear reactor between my legs, the heat generated by the engine is the most I have ever experienced. In cold climates this may be an advantage, but here in Qld it is way too hot and contributes to rider discomfort.
Engine and fuelling - ST1100
My 11 had Staintune exhausts which gave a nice V8 style rumble. My 11's engine had a little bit of Honda V4 character, like my old VFR750.
I found the 13, with standard pipes, very sterile. It reminded me of the Jetsons car with nothing but a whistling sound. I also found the fuel injection to be very jerky at slow speeds in 1st gear which got on my nerves. The 11 was always smooth.
I guess on paper the 13 accelerates quicker than the 11, but I wasn't blown away by the 13. Both will have the front wheel hovering over the bitumen with swift acceleration in 1st. Neither has the punch that my current BMW 1150 has.
1100 wins this round for smooth fuelling and at least having some character.
Handling - ST1100
Going against the grain with this one. I was a better rider when I had my 11, having not really ridden since I sold it. I used to ride the twisties on the 11 in comfort with no issues, accepting that the bike is designed for touring more than scratching. The 13 does turn pretty well for a fat heavy bike, but I did find the pegs touched down pretty quickly. For this reason I pick the 11 to win this round.
Luggage - ST1300
I always hated the way the panniers fit on the 11, and found them to appear slightly cheap and flimsy. The 13's panniers are a weird shape but they do fit in a nicer way. Capacity is probably similar, I wasn't able to compare. The 13 also seems to have a metal tank making tank bags easier to fit. The engine heat makes the fairing compartments on the 13 really hot, so their use is limited compared to the 11.
Brakes - ST1100
I had a non-abs 1100. The brakes were nothing special but did the job.
The ST13 should have better brakes with abs. However I conducted a braking exercise and was surprised at how early the abs kicked in and how long it let the brakes off for. I presume this is due to the abs system being a pretty old design now. I didn't like it. Braking prior to abs was nothing special.
I can't comment on maintenance. I found the 11 to be pretty easy for the basics, the fairings of course needed to be removed but it wasn't too painful from memory. I didn't do any maintenance on the 13 so can't compare. Both are reported to be very reliable. Nor can I comment on pillion comfort having ridden solo on both.
In terms of equipment, both bikes are pretty much basic motorcycles. No modern tech here. Both have stupid tyre sizes, but as long as someone makes a decent tyre that fits that's pretty much irrelevant. I don't know what tyres are still available for the 11 but the 13 I rode had decent Michelins, PR4 I think.
I was expecting the 13 to be better than I found it to be. If I'm honest, I wouldn't buy either bike now. If the only 2 bikes left in the world were an 11 and a 13 of similar age and condition, I think I would have to choose the boring looking but better riding 11.
It's such a shame that Honda hasn't updated the ST (that CTX thing doesn't count, it just looks like a crashed ST1300). A modern, lighter ST with more grunt, less heat, decent abs, more comfort and loaded with reliable tech would probably give Honda another bike with a 10+ year showroom appeal.