Both are equally stellar. 1 plays like a typical spaghetti western while 2 plays like a western drama of sorts, so you’ll find the tone a bit off-putting at first and the story doesn’t carry a lot of the heft that 2 did. Mechanics such as Honor play almost no role in the story so it’s a more linear experience, too.
When it comes to gameplay, you’ll most definitely enjoy 1. I’d say the first game plays a bit better; the controls are more streamlined, and I found myself making a lot of mistakes when it came to 2’s weird interaction menus and such, so it’s a nice change of pace. Aspects such as hunting and side stories are naturally not as fleshed out, but that’s up to personal preference. They’re still pretty good and engaging.
If you ever wanted to pick up RDR1, now’s a great time. We long heard stories of how hellish the development of the game was, so it being available on modern systems is a great achievement. We have yet to see how it would perform on the Switch however.