Buying new mac - faster i5 vs slower i7?

[gnilrets]

I can't seem to decide between the following systems. Both are 27" iMacs.

i5 Option ($2050):
3.60GHz Intel Core i5
4GB 1333MHz DDR3 SDRAM - 2x2GB
1TB Serial ATA Drive
ATI Radeon HD 5750 1GB GDDR5 SDRAM

i7 Option ($2200):
2.93GHz Quad-Core Intel Core i7
4GB 1333MHz DDR3 SDRAM - 2x2GB
1TB Serial ATA Drive
ATI Radeon HD 5750 1GB GDDR5 SDRAM

So they're pretty much identical except for the processor and the price. The new i5's have both hyperthreading and turbo boost just like the i7. So it seems like I'd be paying an extra $150 for 2 more cores of comparable quality. Seems like a good deal! However, the i7 clock speed is 20% slower, so for many apps that don't utilize multi-core very well, the i5 should be significantly faster. Furthermore, for the apps that do use multi-core well, performance may suffer a bit since I'll have less memory per core and would likely have to buy an extra 4GB Ram soon (my rule-of-thumb for the last 4 years has been 2GB/Core), raising the price by another $140 (crucial.com).

So right now I'm leaning toward the i5. On the other hand, I'm not going to be able to afford a system like this for at least another 4 or 5 years, so maybe the i7 will keep it going longer?

Any other differences between the i5 and i7 I should be aware of?

 

[Hellhammer]

i7 goes up to 3.6GHz with Turbo Boost. The two extra cores are definitely worth it in the long run and single-threaded performance is nearly the same due Turbo. Only reason I would buy i5-680 instead would be if your usage was heavily work related and most of the apps were single-threaded and CPU intensive where the extra 266MHz that i5-680 offers would be needed

 

[englishman]

If you look at Geekbench i7 870 2.93 will be faster even in single threaded tasks. Go for i7 definitely.

 

[xraydoc]

If you look at Geekbench i7 870 2.93 will be faster even in single threaded tasks. Go for i7 definitely.

Agreed. The i7 is the better buy.

 

[LoneRider]

Another option is the $1999 quad-core i5. It gives you the extra cores and boost along with the better graphics for less money than upgrading the dual core version.

I don't whether for most purposes the extra speed of the i7 quad is worth the $200 price difference over the quad i5.