What's the diff?

I'm new to ukes, so this is likely all in my head. I have an inexpensive Oscar Schmidt, and a nice Mainland, both tenors. Why would it seem easier or more comfortable to play the Oscar? Not sure how to articulate this, but things flow better and I make fewer mistakes on the Oscar. They both have same strings too. Thanks all.

Could be the neck profile fits your hand better. Or better setup (lower action) on the OS. Or balanced a better for you. Or it's all in your head.

No need to second guess what you're experiencing. Oscar makes makes a quality instrument for an overly fair price to what you actually receive in build quality and playability. While I love my Magic Fluke and Kala Ukes , I give my Oscars an equal amount of playing time.

Enjoy your O.S. Ukulele!

everyone likes something different - what feels right for you might not feel right for another

All ukes are unique!

All ukes are unique. Sometimes you find that you "click" with one special instrument; other times you play a bunch of instruments and don't find that special one for you.

If you played a bunch of Oscar Schmidt ukes, you might find that some of them are easier to play for you than others.

To me this is one of the fun parts about test driving ukes when I am in a store or visiting uke friends.

The thickness of the neck may make a difference. Or the smoothness of the neck. The action does make a difference. String tension will make a difference. Maybe the frets are dressed better on your Oscar Schmidt than on your other uke. Maybe the shape of the body is more comfortable on your Oscar Schmidt.

Sometimes when you play one uke for a while, you really get to know it very well and you learn how to make it sound great, how to play it well. This is just a matter of really learning the instrument and understanding how to bring out the best in it.

Interestingly, I've been wondering that exact thing myself lately.

I would think it is what ubulele said , It is the width of the neck at the nut. Thats one of the reasons I like Martins , they are a tad wider at the nut than alot of other ukes.
That width neck feels more comfortable to me.

It is all very personal. I have a Mainland tenor and I have not found anything that feels better in my hands and I have tried and keep trying big name ukes ($1000 & up) and none of them really do it for me. It is all magic.

The set up of the Oscar Schmidt may be to your liking over the other one. The string height and spacing, the way the neck feels in your hands, the frets being nice and smooth on the ends. And also, the actual strings may be a brand that feel really good to your fingers.

Did you get the OS first?
My first uke was a Kala. My second uke was a Pono.
At first, I thought the Kala was just more comfortable, but the more I played, the less I thought that.

People often say they know what they like, when really what they mean is they like what they know.
Familiarity is often mistaken for better or more comfortable.

Then again.. some times things are just more comfortable.