Arguably the Porsche has better initial acceleration. So 0-40mph or so is likely slightly faster. From then on the P1 quickly catches up and becomes quicker. But, I think it does not matter since the P1 can likely take most turns at considerably faster speeds than the Porsche in the first place, which will completely negate that benefit it has...
We will see...
I really didn't plan or want to getting into this discussion (everybody has an opinion).
However, I think your looking at this strictly through a McLaren's fans eyes (as I understand). No problem with that. That's the joy of forums like this. Regardless of who's faster on what, I just wanted to say this/'Food For Thought':
I think the 918 will be faster 0-60 than the P1.
If a 3600 lb, 550 HP/550 Torque 911 Turbo S can go 2.4-2.6, what do you think a 3600-3700 lb, 900 HP (940 ftlbs) 918's gonna do? I think the 918 will be faster in the 1/4 mile as well (though not as big as in 0-60). Due to weight, and the decoupling of the front motor above 146 mph, I feel the P1 will be faster above 1/4 mile and on longer straights.
As far as cornering: Don't sleep on the 918. Everyone drivers that's driven it, virtually states it has some of (if NOT THE) best turn in and exit they've ever experienced on a road vehicle. It can supposedly corner at 2+G's as well. This is due to it's extremely low COG (the lowest out of the 3 Hyper-brids), 4WS, 4WD, Torque vectoring, and it's enormous torque, which dwarfs the other three vehicles. The 918's aero package and chassis, is nothing to sneeze at as well. I know McLaren's good to. But I don't think your giving the 918 it's due credit in this area.
As far a the ring: I think McLaren is unfortunately setting up many of it's most passionate true believers with disappointment. This 6:30ish time that Autoweek mentioned "from a source" sounds sheepishly like the 6:30 time mood board fiasco of several months ago. How could a team, that could barely hit 7:04 (and others say it was even worse than that), now talk 6:30 ish times again? And I know many here believe it, cause it's McLaren. However, that remains to be seen (especially if McLaren's adding sector times, for a vehicles which may have a compromised Hybrid drive train to begin with).
The last we heard, McLaren was to attack the ring again with new Pirelli's. I don't think it was 'Porsche-like sandbagging (the reputed 7:04 time)', cause obviously McLaren wanted to make some sort of big announcement several weeks ago, and did not/hastily aborted it. Aren't they supposed to produce this car soon as well? Lol
I'm not sure, what McLaren's going to do as far a ring time. However, it seems like an unnecessary obsession with them from my perspective. If they do beat the 918's current time, they will have to SMASH IT, cause no one will care if they do. "Been there, done that" is what many would feel. Plus, Porsche's already reaped the fan fare, adulation, sales and benefits from the worlds motoring press at Frankfurt. McLaren would have to make it significant, for Porsche not break it back as well, as they already been serving notice this week. However, I don't know if McLaren can/will? As FTYL (and others) said earlier, "We'll see?" Good Luck to them though. Either way; I'm sure they P1 will be a great car, and please many of it's fans for years. I wish them well.
I'm not sure what we can gauge from the LaFerrari, when it's not even known to have an advanced prototype yet (and as WT Doom mentioned, ' if we can we believe it's specs')? I guess, we'll have to see on that one as well? Not much to say.
The time for talking is over with these manufacturer's Now they just have to produce, with their working vehicles. Too many undelivered promises so far. I'm also curious to see if the both the P1 and LaFe come in at over 3400+ lbs as Motor Trend expects them to?
Once again; I'm not saying what the P1 won't and can can't do (that's up to actual performance). This was just food for thought.