Welcome to the forum!
To address your questions:-
1) Short answer: yes. On site experience is always an advantage. Having knowledge of how things fit together can make your designs a lot more efficiently. Or at least, make it easier for the chaps that have to put it all together.
2) I enjoyed my time on site. Having to solve real time problems puts you on top of your game and the variety of locations allows you to meet some interesting people that you wouldn't have access to, being consultancy/drawing office based.
I had a great site experience but others I know didn't. They couldn't take the pressure of being the "go to guy" so it's not for everyone.
If you're not planning to settle down anytime soon, stick with it. It's great experience for a young engineer.