Sides Left/Right - Less physical demanding

I had a look at my heart rate stats from games where I played left and games where I played right and, on average, playing on the right has it lower by roughly 15bpm.

So, this is a sport so there's always going to be an element of movement, but it depends on the opponent. I know older people who play and barely move their feet, they either have incredible court placement or they play against other older people who barely move, and they agree not to play drop shots before the game. If you're looking to play more generally, they're better off playing on the right. Left-sided players are expected to cover 65%+ of the court, as their forehand is in the middle of the court, so it's easier for them to hit balls that come down the tee. As the other player on their team, you should be ready to cover a lot of ground, particularly if you make it to the net. If your partner doesn't like moving when they're facing forward, they really won't like moving backwards, so chances are you'll be covering for them when they get lobbed. Slow the game down, be prepared to play a high lob back to give yourself time to get back into position.

I think this depends on who you play with as partners and who you play against as opponents and what you do during the play. I play mainly on the right and if my partner says he wants to cover the middle, then as the left side player they will be moving more. I also have left side players who want to get in the right side of the box to smash, vibora, bandeja etc time to time, that means they have to move extra and rush back to their initial location etc. However that really depends. I had matches where I was more comfortable on left due to not having to move too much because I had been put on freeze, and I had matches where I was exhausted when I played on the right because of Chiquita + Lob repetitions. (I am rather short so I get punished in the land of the tall people haha) Long story short: Amount of movement will depend not only your team's playing style but also the opponents..

My perspective has been so far that left side has middle on their forehand, so they are the one to cover it and there's a bit more running for them. If I'm paired with someone worse than me, I'd rather take the left to maybe be able to save a few balls in their field that they don't think about running towards. 

Right side, right handed 

That really depends on how the partnership plays, but if the pair are both right handed and playing correctly then it should be a bit easier on the right. This is because you can defer a lot of middle shots to the left sided player who can then hit more attacking forehands

I would also say that the left side is more intense at my level, but judging by how much Chingotto moves, the right side can be quite hectic too if your opponents know how to make you move.

Left side player usually runs more because they cover more court: left side plus + the middle with their forehand.

Right side, but in the end it doesn't really matter in the long run. Mobility plays a key role in padel. The opponent will learn that you can't move as well, and suddenly all the shots are aimed at your half, just out of reach.

I play both roles and when im tired i prefer playing right because i need to cover a lot less of field.

Depends on the pair dynamics, opponents play, match and even on the day

To me the left side is easier to play despite covering more court. It's intuitively less taxing to hit shots from the left. High quality shots from right side takes a whole lot of foot work to get in position and execute properly. You can't just "reach" a bit for balls. 

With typical roles, backhand player exert more energy, because he takes most of the overhead shots and has to cover more court. But if you look at forehand players like LeBron and Coello, they probably exert as much energy as their partner.

If you are the weaker player, you will get most of the balls and you will run most of the game, doesn’t matter the side.