I mostly ride for fun and exercise. I am trying to push myself to increase endurance but I am not a racer by any means. Currently have a GMC Envoy (cheap, looks like a road bike with MTB gearing) and a 90's Raleigh M40 step-thru MTB. Both are yard sale finds. I ride 95% pavement with the occasional grass, dirt or gravel. There are some pretty good hills in my area. I find the ride of the Aluminum Envoy with drops and aluminum front fork to be hard on my wrists sometimes (our neighborhood has it's share of potholes). So I end up on the MTB most of the time. I don't do enough off-road to really need a big knobby tire so I have been thinking about a hybrid. This weekend I went to see a 94 Schwinn Crisscross. It was in like new shape with new tires but a 17" frame. For $50 I bought it anyway. When I got home we found it fits my wife perfectly. So she is retiring her 92 Schwinn Mirada sport step-thru. I am still looking.

Locally on CL I see a 94 Cannondale H300 Aluminum W/ ChroMoly fork 22" frame asking $200
also on CL but an hours drive away I see another Schwinn Crisscross ChroMoly 18" or 20" frame asking $70

I am 5'10" and 48yr male

Provided they fit, would of any of these potentially be good bikes for my riding style? Or should I just get some smooth tires for one of my existing bikes. I still like to try to go fast on occasion but mostly looking for decent ride with ability to get to muscle fatigue before joints are beat up.

I have no real opinion on the possible purchases.

Smooth tires on a mountain bike are always an inexpensive alternative to get quicker rolling if you aren't doing true mountain biking. In fact, some early hybrids were not very different than mountain bikes with smooth tires. I have a Raleigh mtb that I have converted to loan to people for rail trail rides, and it has worked very well with smooth tires as a hybrid. For the one I use, the suspension fork was shot, so I replaced it with a rigid fork to savbe weight and avoid energy loss. If the fork was functional, I don't know whether I would have converted or not.

Concerning your other bike... When you ride the Envoy, do you ride on the hoods, or in the drops? Riding in the drops is uncomfortable for many people until they get used to them. In addition, for many riders that use drop bars, the benefit is multiple positions. If you watch a road bike race, the majority of the time you will see the riders riding on the hoods and bar tops more than in the drops... Just something to consider.

I pretty much ride the hoods. In fact I have some old Shimano RSX brifters I just cleaned up and re-lubed to possibly install on the Envoy. I'm sure my fitness level, or lack of, is a factor for discomfort. Could be the cheap frame or Aluminum fork as well IDK.
I was already considering going to smooth tires on one of the MTB Then I saw some nice used 700c hybrids, so I thought I would investigate that option.

I definitely lean toward 700c in hybrids... my primary ride right now is a 2011 Trek 7.3 FX, and it rolls very nicely, and isn't harsh, in spite of the aluminum alloy fork. But, I bet it would be even smoother if I had a higher end FX since they have better forks.

Put smooth (almost slick) tires on your MTB and call it good. A 700C hybrid would work too.

I picked up a 1994 hybrid in 2008... still had the store price tag on it, so practically a time capsule. It had flat bars, twist shifters, etc. It's evolved considerably to something resembling a light tourer, including drops with bar end shifters. I ride the hoods most of the time, but when I get in strong winds the drops are nice. As you found with your wife's Schwinn, you can get some great bikes on CL. If you can find one in your size, you might be happy with it. In the meantime, consider smoother tires on the MTB.

At 5'11" a 22 inch frame will be too big. I'm 5'9" and a 17.5" frame fits me very well.

So is $200 in the ballpark for this 94 Cannondale H300. It looks nice but not mint. Some add-ons.
Vintage Cannondale H300 Hybrid

not real sure on the frame size. I may go look at it. I am used to old chromoly yard sale prices, so $200 just seems high to me for a 90's bike. but if it suits me it might be worth it.

Not a bad price however condition and fit have yet to be determined. Remember it's got 7 speeds in the rear while most new bikes have 10. And if quick rolling is your goal those tires should be swapped.

1993 Cannondale H300 - New and Used Bike Value

$200 is a bit high based on expected value for a 1993... which is $133 if like new... I didn't see 1994 in their listings... but the values would be similar.

However, if I was in the market, and it fit, I would probably make an offer... With the computer and rack, I would make an offer of about $130 and be willing to go up a bit. Value is dependent on market as well, so it may be worth that in New York.

While I was contemplating, Cannondale purchase price + new tires + possible shifters, cables. etc. Cannondale sold.
No biggie. I bought 26x1.5" street tires for my old bike. Liked the ride so much I decided to go ahead and replace the original shifters that seem to be stuck every spring. So after adding new tires, new Altus 3x7 shifters and cables, and cleaned and wax plus elbow grease with Mother's aluminum polish; it looks like this.

That looks like a pretty decent bike. I think you will outgrow it - which is good news. My feeling is you want to buy a bike that will make you want to ride more and make you become a better, stronger rider. In short, you want a bike that will encourage you to out-grow it. And I think this bike will do that. Have fun!

Sizing is different for Hybrids/MTB's and road bikes... that Cannondale would be way to big for you.

I never did actually meet with the guy who had the Cannondale. I had to cancel once. when I tried to reschedule, it was too late. Charts show me at 18"-20" on a MTB frame. That sound closer?

You're probably right about me outgrowing it someday. I still enjoy watching Craigslist for the possible deals, but for now this rides and shifts better than it ever has. My town is riddled with poorly repaired potholes. uneven expansion joints etc. This hybrid makes it seem smoother than my road bike. I would like to get my endurance up and then work over to some road biking too.