Not quite. The SB will definitely OC better
That's not true at all. SB and IB overclock very similarly. If anything, Ivy actually overclocks better than sandy, because of the 22nm process and cooler chip.
But a non-delidded Ivy Bridge, you will have prohibitively high temps above 1.35v, so you got a lot of people saying it overclocks worse than SB. But the problem is that with sandy, you start running into votlages that definitely degrade and even kill the chip above 1.4v. Whereas on Ivy, degradation/death is very rare and 1.5v is the lowest minimum voltage you really hear about.
Both Sandy and Ivy bin exactly the same, over 50% of them can't hit over 4.6ghz on a reasonable voltage. But ivy is much easier to work with because of way lower temps, a much cooler chip (if delidded), and the ability to push up to at least 1.55v for 24/7 overclocks. And you need to push past 1.5v for 5ghz unless you have one of the 1% of ivies out there that is really, really, really golden.
Well there are a few reasons i wouldnt mind going with the 2700k (which the special is over now)
1) I hear that BF3 is one of those games that can get more fps from hyper threading (and that is the game i play most)
2) Supposed better mulittasking....i like doing video editing while watching a movie while web browsing etc.....
3) Better performance during video editing
4) Better OCing capabilities to 5.0ghz
5) More testing = FUN!!!
1. it's not significant, your gpu is where you BF3 frames come from. You would only want to upgrade your CPU if your minimum fps was low (not just in BF3, but any game). If you struggle in bf3 when all your graphics are on low settings, that's a sign that your CPU is weak. If you struggle during intense moments of BF3, that's a sign your cpu might be weak (but be aware many games these days run fine but can have moments where it brings any cpu to it's knees, even the 3960x).
2. There's no better 'multi-tasking', that's simply not true anymore with how efficient the scheduler is these days. This was true like 10 years ago, and it was more like "Now with 2 cores, you can run windows on 1 core and internet explorer 2 on the other!". Multi-tasking is all about your RAM now, not your CPU core count... And web browsing is nothing, if your demands are vdieo editing while watching a movie and browsing, then an athlon ii x4 would be more than powerful enough for your needs. Also be aware that a lot of video editing and streaming and other multi-threaded applications, while may appreciate multi-threaded performance, they are often bottlenecked by something that is single-threaded. For example, video encoding, streaming, that's very multi-threaded, but capture is a software problem, not a hardware problem, which basically means the best streaming CPU is the best gaming CPU (which means cores don't matter).
Also be aware that most multi-threaded applications, are not that multi-threaded. Most of them prefer better IPC way more than more threads still. It's only a few outdated, older versions of certain programs, that actually really care about thread count.
And hyperthreading just means 2 interger points and one floating point, it's not like an extra core. In threaded applications it's like a 20-40% performance increase at best.
3. What video editing do you do? Not all programs utilize hyperthreading. The i5-3570k is already extremely good at video editing...
4. Your 3570k will overclock 'better' than an i7 sandy bridge as long as you delid, but sandy bridge is quite restricted when overclocks are concerned unless you got custom water and a great chip.
5. well in that case go for it, you can always sell your cpu for what you paid for it and buy a new one. Computer components are like cash, they are fungible.
It sounds like you really just have a bad chip and want to get a good one. Just sell your i5 on ebay and use the money to buy a new i5 (you should be able to sell a used i5 for about what they cost to buy brand new). Repeat until you get a good clocker.