I can never get a bead on where diminishing returns start with this stuff? At what point do bikes get good and then improvements from then on are just icing?
Diminishing returns start at the absolute bottom. If you're interested in a threshold, that'll depend on how much you care and how much money you're swimming in.
I used to have that problem for years. Left knee would hurt after 1 hour ride, even if I set gear to normal and on a straight road. Hence why I started warm up and leg excersise. Stretching mostly and rope jumping. I wear protective cover on left knee just in case, but I have not faced any serious problems since.
I'm not talking about knee pain. I'm talking about when I'm huffing and puffing and the
driving muscles are on the threshold of what they can put up with over significant distance. I push toward the edge far faster if I'm cycling hard at a low cadence, and once I'm already fairly exhausted, high cadence makes it physically possible to keep up better power and speed.
Is a 700x35 tire versatile? It's mainly for commuting (2 miles each way) but I'd also like to go on longer rides with it (10+ miles). Suburban and urban riding.
I'm little worried that a size 35 tire starts to get into a territory where inefficiency becomes an issue?
Would a 32 or 28 be more up my alley? I'm looking for a good balance of efficiency and also puncture resistance.
35c will offer a slightly cushier ride and function better on less ideal surfaces. 28c will accelerate slightly faster due to less rotating mass, and will roll slightly more efficiency on smooth tarmac.
Personally, I occasionally pick my 34-pound hardtail mountain bike when I set out on a half-century road ride, just because I might feel like being in that saddle. Even though I have two road bikes.
For some recreational riding here and there I definitely wouldn't sweat the difference. If you like the idea of 35c tires, go for it.
Straight of the bat, I assume endurance bikes are not fast, which is most likely very untrue. I like to go fast, so I think a performance bike would fit me, but at the same time I like comfort.
Are performance and endurance road bikes extremely different from each other when it comes to speed and comfort?
My Fuji America is a touring road bike made in the 1970s. In its present configuration (i.e. racks and fenders and such) it weighs over ten pounds more than my new Emonda ALR racing bike. It uses 700x28c tires at substantially lower pressure than the 700x23c on the Emonda. It has a less aggressive posture, designed for comfort, with inferior aerodynamics. It has a friction-shifted 3x6 drivetrain, versus the Emonda's 2x11 105.
The difference between America and Emonda is
vastly larger than between the bikes you're looking at, which are all essentially racing machines.
How would I describe the ultimate performance difference between these two machines? Not particularly huge. If my Strava results so far are anything to go by (it's admittedly not much sampling), I can sometimes manage a few percent faster up hills on the Emonda, with flats and downhills being almost a wash.
Get out on the road and ride and you'd be hard-pressed to find much significant difference in performance between the bikes you're looking at. And even if you did find significant difference, you could probably make it vanish by moving a small bottom spacer to the top of the stem.
...Buy a bike which fits, and which feels the way you want it to.
Strava makes it easier since it tells you in hard facts how fast you take those hills. If it weren't for that, I'd still struggle uphill with far too high gears since it "feels" faster. I ride with a friend who has been active cycling as long as I have, and he still does it the hard way, no matter what I do or say (he does not use Strava).
