5.3 vs LS1?

[chevy72blu]

Hey folks,

In my hunt for a 5.3, I came across a local guy with an LS1/4l60e combo (complete) with 60k miles. He is actually interested in other motors/other stuff I have laying around so I could trade straight across (cash value around 4k). Since I planned on spending around $3200 for a motor/trans/harness/pcm flash this is a step up in budget but the trading makes it a lot easier.

My question is - is there any reason NOT to go with the LS1? It is my understanding that "go fast" parts are cheaper for it, but my goal with this build is just to have a reliable DD. I am aiming for 20+ MPG in my mostly stock 72'. Of course, we all say that... and then wish we had more power when standing on it

Is there a significant difference in power between the LS1 and 5.3 Vortec? Is there a significant difference in gas mileage? I know that the aluminum block is lighter, but that kind of seems like attacking the mountain with a tooth pick considering how heavy the beast is anyway.

I did a search, but didnt get answers to my specific questions. Sorry for the dumb ones folks... This is all new to me! I hope everyone enjoys their Sunday.