Several points I'll reiterate. On my trip back in 2012 I was in better shape than I could ever had hoped to be in. When I left home I had already ridden over 12K miles for the year, an I left in early to mid August. I knew I should easily be able to pull off 160 miles a day...OOPS...that 160 miles a day unloaded. I got on the trip and learnt the difference between unloaded and loaded riding. Talk about the shock factor. I was still riding along doing 120 miles a day and still averaging around 17-18 miles per hour but I wasn't going anywhere like I thought I should have been able to given what I had been doing back in mid July. Their can be a rather dramatic difference in speed and comfort when you make the shift from unloaded to loaded riding. Expect it to occur. I didn't and got the rude awakening instead. LOL You'll have the extra speed helping to pull you down the hills but you'll also have the extra weight keeping you from being able to climbing the hills which will slow you down. I would say the difference between the two is probably inconsequential as they probably come close to equaling out but the extra effort you have to put in when climbing will wear you out faster.

When I ride normally versus when I ride loaded I'm typically riding the same speed, unless gravity is a factor. Since I ride predominately single speed I'm always maintaining right around the same cadence. I think their is a lot that can be said about everyone having their optimal cadence range. I see it right now as I've been spending the past several weeks trying to puppy the bike along into spring before doing any major work to it. I'm right now riding a 38x22 and I can't stand it. It's WAY too small unless I get a day where the air density is flat out sky high and I just can't push through the thick air. I've had a couple of those over the past week or two now...they suck. I'm someone who likes the bigger gears. I typically tour in a 52x17 or 52x19, irregardless of terrain. I don't spin worth a crap so I need something that keeps me pedaling along at slower rpms for it to even feel like I'm make any kind of headway. Right now anytime I'm on the bike it feels like I'm going nowhere...real fast...err, slow. Their is no effort to spinning the pedals whatsoever and have the time I have to stop pedaling and let the bike slow down so I can keep any kind of pedal pressure. Can't wait for spring to get here so I can get rid of the salt/sand/snow/slush/etc and get the bike back in decent working order and swipe back up to a 52x17 once again. Boy, I'm drooling for those days.

I think the best bet is to find the pace you like riding at and stick to it...either loaded or unloaded. The only way you change the pace is when the conditions, weather or topography, changes. The extra weight only slows you down because it wears you out faster and not because it should make you go slower.