I know I have not followed the conventional wisdom, but I decided to put my pilot training on hold while I build my RV-7A. I thought about it long and hard, and here are my reasons.
It's a big commitment for each one. I do not have the time, the money, or the focus to try and do both at once. I realized that even if money wasn't an issue, if I try to do both at the same time, I won't do either one very well. Either that or it would take me forever to get both tasks finished. You've heard the old saying "Divide and Conquer". If you divide yourself, you'll get conquered. As someone else mentioned, if you have a home, family, and marriage that you value, you will run into serious conflicts. Plus, I'm still working and trying to run a business. It's hard enough doing just one of the two tasks and keeping everything else in balance.
Next, building an RV is a process that will take most people 4, maybe 5 years to complete. Many go longer, or much longer. Life gets in the way, as they say. I'm in my 8th year as I near the finish line on my RV. I saw other builders' piloting skills get rusty as they put flying on hold while they build their RV. I didn't want to go out and spend all that money and do all that work and training to get my license, just to put it on hold while I spend 5 years building my RV. So I decided to just wait and get my PPL started as I near the finish line with my RV. It's a decision I'm glad I made.
Course, I've always known that I love flying and there is no doubt I will enjoy my RV. I've wanted my own airplane since I was a child. A few close friends have taken me for a ride now and then, and it really keeps my dream alive and keeps me motivated.
Now, if money isn't an issue, or if you already have a plane you can fly while you build, or if you're retired and have lots of time on your hands, that's a whole different scenario. But I did not have those options. It will take you longer to build an RV if you are flying at the same time. There have been many, many beautiful sunny Saturdays and Sundays when I was looking up at the sky, wishing I was up there flying, but instead, I was deburring metal parts, dimpling sheets of aluminum, or hammering rivets. Flying would have been more fun, and if I had been able to, I would have been up there. So my RV would have taken a back seat and it would take me even longer to get it finished. I have several friends in that situation right now. I did get a lot of work done on those days, and it was motivation for me to keep at it and get this thing finished, so I don't spend all my sunny days on the ground, looking up.
So that's my input. I hope it's helpful. Consider all your options and your real life situation, and do what's best for YOU. Either way, if you end up with a PPL and an RV to fly, you win! The order you do it in won't matter much at that point.