Which size?

Not sure how you are going to decide, but large gets my vote, plenty big for a family and too big for quick cooks, the Mini Max is my go to now for weeknight cooks. Let us know what you decide!

Hard choice - both are very capable.  I started out with the idea that I would only have one egg.  I chose the XL, and have been extremely happy with that choice.  I mostly cook for 2 also.  Having the capability to easily put on veggies at the same time as meat is valuable.  Also, when you want to do a large cook, the XL is perfect.  Can you do it on a large? Yes.  It's much easier on an XL.  I've never had any problem with maintaining a low temp with the XL - it's easy once you get the hang of it, and figure out the vent settings.  There isn't much difference between the time it takes for either a Large or XL to get up to temp.  After 2 years I decided to get a Medium.  I love the medium, and use it more than the XL.  But when I need the space, the XL is the go-to cooker.  Last night I did a fairly large tri tip, some corn and Brussel Sprouts.  Easy on the XL, it would have been more difficult on the Medium.  To summarize though, if you are only going to have one Egg, buy the largest you can afford.  Virtually no one with an XL regrets that they didn't buy a smaller Egg.  Whatever you get, you will have a great time, and cook some great meals.  Enjoy!!

Regarding when to buy, if you can get to an eggfest you will get a very good deal; full warranty, discounted pricing and the BGE has only been cooked on once (at the fest) if that.  FWIW-

Rad5 said:

Aside from just having more room with an XL, how does it perform compared to a large? Does it take longer to heat up? Is it too big for week night use? I like to do slow and low BBQ and I have read its hard to maintain low temps in an XL. This is a big purchase for me and I want to make the right decision.

Not sure if you already mentioned it, but what (if any) are you cooking on now?

Rad5 said:

I have nice gas grill that I will keep. I also have a 22" Weber Kettle and a propane smoker that is ready for the scrap pile. I was thinking the BGE could replace the smoker and Weber. We don't use the weber that often because its hard to maintain temperature and takes some time to get going... even with a chimney starter. We do like the flavor of charcoal grilling but don't ever do any during the week. I am hoping the BGE is something we'll use on week nights.

I have an XL and it's just my wife and I. It's my only grill/smoker and have no need for any other. How many people you're cooking for really makes no difference.  For me, the XL is about using a lump reducer and having direct (in the center of the XL) and "indirect" around the outside ring for potato wedges, corn and other things I don't want blasted with heat when I'm grilling.  I use a $8 electric starter and I have food on the grill in 16 minutes from the time I first open the lid (8 minutes with the electric starter in the lump, stir coals, then 8 minutes with the lid down to get everything going good).  I found the XL extremely easy to use right from the beginning, the key is to pay attention when you're firing it up and don't overshoot your desired temp.  It's easy to bring the temp up, not nearly as easy to bring it down once you've overshot your desired temperature.
Get the XL and enjoy yourself!