This is it, Kieron Gillen's favourite bit! Anti-aliasing and lighting effects may well be important to some, but a console first-person shooter lives or dies according to its frame rate. A smooth refresh rate helps immerse you into the game world, but crucially, it's the game's visual feedback from your commands on the joypad; its handshake, if you will. Most console shooters aim to operate at a rock solid 30fps, and F.E.A.R. 2 is no different.
This is where things look very dicey for the PlayStation 3, but the difference isn't immediately apparent. F.E.A.R. 2's initial stages take place in small, confined environments - so plenty of geometry to cull that keeps the frame-rate acceptable, if prone to the odd inconsistency. However, once you leave the hospital setting of the first bunch of levels, and take your first steps out into the blasted city, things take a turn for the worse.
F.E.A.R. 2 is v-locked on both platforms, making frame-rate analysis very easy indeed if you have lossless digital captures of your gameplay to hand. You simply compare one frame to the next, and count the duplicates - a dropped frame will be digitally the same as its predecessor. In a locked 30fps game like this, you'd expect every other frame to be identical - where that pattern's consistently broken with additional dupes, that's where things get nasty.
So, here's an excerpt of gameplay taken from the same area on both 360 and PS3. In an ideal world you'd want identical video from each source, but this isn't really about engine performance so much as the kind of consistency in refresh rate and response that you get on 360, and that you don't get on PlayStation 3.
To explain how the graph works, the centre is the frame currently being analysed. The frame rate counters in the corner are updated as an average every half-second and the graph lines are similarly calculated as averages over a set number of frames.
What you're seeing here is that while the 360 code is fairly static (across the whole clip, the average is above 29fps), the PS3 version drops down very frequently to 20fps. By the very nature of how v-lock works, typically a non-consistent frame-rate is quickly shifting between 20fps and 30fps, resulting in a jerky update (see: BioShock PS3). But what this graph is showing is that in many cases, the refresh rate drops down to 20fps and can stay there for quite some time, before recovering.
In short, the gameplay is compromised quite severely because the more intense the action, the more likely it is that you'll get less feedback from the controls. In the midst of a hardcore shooting match, the last thing you need is a numbed response to your commands. PS3's graphical shortcomings don't have much impact on the fun you'll get playing the game, but this kind of poor performance definitely will.