Hello,
As a commute bike I have a old 10 speed and the other is a full suspension giant MTB. I don't like the 10 speed for 2 reasons
1) it is a very rough ride
2) I have to climb some major hills and it don't have a wide gear range like my MTB does.
My MTB on the other hand has full suspension and I lose a lot of momentum cause of it.
( my commute is 31 mi. R/T )

SO MY QUESTION TO THE COMMUTERS.
If I buy just a regular MTB with no suspension and put on slicks. Is it a big difference between MTB and 10 speed as far as resistance goes? I want a softer ride. But I could live with A road bike with more gears. Thanks for your thoughts.

Yes! There will be a huge difference between a multi-geared MTB with full suspension and a multi-geared MTB with a rigid fork.

The rigid forked MTB with slicks will accelerate faster and maintain its momentum with less energy being applied.

PS.

Of course, that all depends upon your terrain. If you're on treacherous mountainous rocky terrain, all bets are off! Gimme my full suspension MTB back!

If you're on pavement, you don't really need a MTB. It will only slow you down!

Yeah slim it is all paved roads.... but is it a big difference between a ridged MTB than A road bike?

I have a MTB with a suspension fork. No rear suspension. I put some street tires on and noticed a big difference over the knobby MTB tires as far as the rolling resistance. I can maintain a speed with easier effort with the street tires on. See if you can tighten the rear suspension up to reduce the lost work due to the compression of the suspension. I also use the lockout, or close to it, on the street on the front shocks to reduce the lost work even more. I suppose the other option is to buy the hardtail MTB and slap some road tires on there. That should net you the biggest gains in the rolling resistance and work put into pedaling I think.

i've found that the major differences between my rigid MTB bikes (2) and my road bikes (4) that i ride everyday, assuming they are set up with the same BB to saddle height and same reach and drop (which they are) is that the MTB bikes are heavier and everything that entails (due mostly to the frame/fork) and are stabler (due mostly to the slack headtube angles). they all use about the same 23-32mm tires, handlebars, pedals and saddles..

I would say for a 31 mile R/T commute with hills you want something that is comfortable, efficient, and versatile. I think you'd want a road bike with fatter tires for more comfort - 32's at least. Maybe a cross bike. I'd personally really hate to pedal any MTB that far on a regular basis, even with slicks...

I would put bigger tires (32mm width) and a different freewheel (14-32T from a 5-speed) on the 10-speed. Boom, problem solved.

(If the inner chainring is a 42T, I'd change that to a 39T or 40T as well.)

If it's a rigid 29er like the Surly Ogre, the difference will be very little at first. However, that's depending upon the distance traveled. As the distance increases, the greater the difference will become. Eventually, weight, tire width, geometry, and aerodynamics, will increasingly begin to factor.