weimaraner or lab retriever?

I'm a Lab person through and through - I've had them my entire life.  I can tell you about Labs, but no recommendations from me!  Every breed is certainly not right for every person.   Based on Emily's brilliant description and from the Weims that I've known (my sister has 2 right now) they are not vastly different from Labs.  It's not like you're trying to choose between a Mastiff and a JRT!
Disclaimer - the following is based on my experience and what a well bred Lab is *supposed* to be.
 
The Good:  Extrememly good natured.  SOOO good with people and dogs alike.  I have never had to give a second thought to my dog's behaviour either in the company of other dogs, or with children, etc..  They are very loving dogs, meaning they love to cuddle, kiss, sit on your lap, and have your attention.  Highly trainable - great for a novice because they will NOT be traumatized by your mistakes!   They recover very quickly and adapt brilliantly.   They are very stable and sound in their temperament, they just do not over-react to things (very easygoing).    Their adaptability is really one of their best qualities.  And depending on your lifestyle - they can do it all:  swimming, hiking, running.  They are also very silly dogs... I'm sure you have the image of the big doofy lab, bounding around, slobbering on everyone.  This is somewhat true!  My dogs have always been much less "doofy" than the stereotype, but they are very happy creatues who are shameless in their joy.  For me, they are the PERFECT family dog because they adapt to the family and are a neverending source or humor and joy.   
 
The Bad (depending on your interpretation):  Remember how I said that they do not over-react to things??  Well the bad side to this coin is that when you correct them, they're not really bothered.  You can almost see them making faces and rolling their eyes when you tell them NOT to do something.  They really seem to enjoy being naughty, it's just part of who they are.  They're "mouthy".  They've been bred to carry fowl gently, yet firmly and are absolute masters at carrying things around.  EVERYTHING.   Quick example.  I was home sick in bed the other day.  In the course of about 2 hours, Slick brought me (and placed all of these items on top of me in bed):  the plunger, a tomato, 2 books, the dustpan,  a sofa cushion, my wireless mouse, a wooden Buddha and 2 remote controls..  They're PIGS.  They will gladly disobey you if there is an edible score involved.   Because of this they tend to be major counter surfers and even if you've trained them not to do it - they can never be trusted around food!   They chew, alot.  The puppy chewing stage that you hear about with most dogs, lasts about 3 years with Labs.  There's no way out of it without some damage to your possessions. 
 
The ugly:  A bored Lab is capable of destroying your entire house.  Much as Emily described, mental stimulation and physical exercise are NON-negotiable!

I have a pretty decent size yard for a large dog, would it be ok that i left the lab or weim dog outside for 8 hours? I'm thinking i could go home during lunch because work is 15 mins away and play with him. But when we get him he will be a puppy and i know that puppies need a lot of attention (age 3-5 yrs). I thought about sending the puppy to a day care but it looks like somewhere like petsmart only takes in dogs at least 5 mths old. 

I wouldn't leave a puppy outside for that long.  As puppies they tend to sleep most of the day anyway as they grow.  About 5 months of age would be the perfect time to send them to daycare.  If you can get home for lunch and let them out it should be fine to have him crated during the rest of the time.  It really doesn't take that much to get them tired at that age. It just seems like it takes a lot because you will be tired from the middle of the night potty runs. Though Scout was sleeping through the night at about 3 months of age.