At least for the 1st 12 months, the console that is released 1st will likely lead in total sales.  The xbox fans will buy the Xbox1 and PS fans will buy the PS4.  But there are lots of people that will only buy (and able to afford) only 1 of the system.  In few years, the sales of the console will likely separate out depending on which system/ecosystem/games are better.

On a side note, Battlefield 4 better have 64 player multiplayer on the next gen console.....

PS4 but i think they will come within weeks of each other. Whether both have global releases in 2013 is another matter all together

I expect PS4 to release a bit earlier but I actually hope they both release in the same month so there is nothing like "XBox only leads because it came first" or something. Hopefully it is a fair and exciting battle :)

XOne cause NFL starts September 5

Needs poll! Also it's hard to say. I think they'll launch together but if I had to choose one I feel like Sony is more eager to get their console out there.

i think the PS4 will release mid november and xbox one comes late november or early december

This is tough.

With the various MS reports that they are "6 mos behind schedule" I've figured they were likely not coming to the holidays, November to be specific.

Well Sony confirmed the "holidays" as their launch. For them that has been November typically, so I expect the same.

However, MS purposefully vague with "this year".

There were also rumors that at one point MS wanted to deliver at the same time as WiiU (reason for sig bet) and then combining that with the 6 mos delay rumor... well that only means MS was pushed out to mid THIS year.. i.e. June/July.

The hardware is clearly finished in Xbox One. Its out and media has their grubby little hands all over it with inside pics and everything.

I'm thinking MS may actually launch early in say September. This gets them out well before Sony and cuts dramatically down on the time Nintendo has post-E3 to build up userbase with their late-2013 titles.

So for now, I'm putting my money on MS releasing first.

I predict they will release both on the say day. It's personal for Sony this time, and Microsoft will stand its ground. It is a battle of egos, and I believe both companies wish to prove to its loyal/potential consumers that the future lies in their vision.

I can afford both systems, but I will wait to buy one first. I am waiting for a few reasons.

I don't know how their subscription policies/online policies will be until a year into the cycle.
Both companies have proven to stumble on the first year of release, best to wait when they're up and running.
Don't know who is making their hardware, I'm not dying to give more of my money to Foxconn.
2nd year games are always better than launch.
Possible temporary price cut for black Friday 2014.
You get a better sense of their vision & dedication a year out. (Promises mean nothing without action.)

Things PS4 & Xbox can do to change my mind on waiting a year:

Promise a 2-3 year hardware warranty, promise a new system if hardware fails or if 1st version is defective.
Have the online service 1-3 months up before release and demonstrate how effective & wonderful it is.
Not made in China. (I know, I'm dreaming)
Online policies on prices need to be written down for consumers for first 2-3 years. (Still dreaming)
Show me why waiting a year, is probably not wise. (Could be a special promotion for early adapters, I don't know)

Both at the same time in US, PS4 earlier in Japan, Xbox One only this year in Europe.

Yes I think PS4 will not release this year in Europe, march 2014 is my bet for that region.

? don't you americans have minimum of 2 year warranty automaticly like us EU people?