I‘ve been down this road and currently own the Day-Date Automatic (or MK40 if you prefer) as well as the Pro.
You get a lot of bang for the buck with the Day-Date and that was my original reason for wanting it. Mine was actually a gift from both sides of my family for my 40th, as well as being my first Omega so special in that sense. It was more or less my only watch for about 10 years and thus you could say I was pretty happy with it. I think it makes a good daily companion. But honestly it’s not even remotely like the Speedmaster Professional; like night and day different.
Although my Pro has a non-scratch resistant Hesalite crystal compared to the scratch-free Sapphire on the MK40 and obviously fewer complications it’s still somehow more interesting. This might sound a bit daft but there is something strangely satisfying about the manual winding experience on the Pro that you don’t get so much with the Automatic. That’s probably true for any number of manual wind watches, but anyway, it’s a difference that’s nice.
If I was going down this road again would I do the same? Probably not. I think I would have gone for the Longines L2.673.4.78.3 first which has a beautiful dial and adds the Moonphase complication.
That would have better satisfied the desire for maximum functionality in a single piece at an affordable price, then add the Pro at a later date when funds and knowledge provide more choice.
Try to avoid being blinded by all the hype; the Speedmaster is a nice watch in most of its forms, but there are plenty of others that are just as fascinating out there.
Take your time, choose wisely, oh and have fun!