Wanting to know if there is a huge enough difference between the two or which is typically better than the other? Not much of a difference in price tis why I ask. Being as blunt as always, letting the title speak for itself.
The i5-2400 has the HD 2000 graphics on chip and is the 32 nm die process. Turbo speed is 3.4ghz and the stock speed is 3.1 ghz.
The i5-3450 has the HD 2500 graphics on chip and is the 22 nm die process with a turbo speed of 3.5 ghz and a stock speed of 3.1 ghz.
The i5-2400 is currently $5 less then the i5-3450 and with the smaller die the 3450 has a lower TDP by 18w so it will consume less watts and give off les heat.
The cost of the motherboard could be a deciding factor since to take advantage of the features of the Z-77 chipset the 3450 would be the choice for that chipset and the i5-2400 would not be able to take advantage of the z-77 chipset's features and would best be suited for the Z-68 chipset motherboard.
For this level of cpu the best choice would be the i5-3450.
It's an i3 an a dual core not a quad core but it does have hyperthreading. However by adding it into the debate we now have a candidate for third place.
You would only pick this cpu if the budget had absolutly no room for either of the other two.
What if I throw in the i3 2120 for purely gaming reasons, what then? Sorry just still debating on the 2120 seeing as it is a very good processor.
Depends on what sort of gaming you want/plan to do.
i3 is a good pick for games that can only leverage 1-2 cores (the bulk of what is out there right now) but i5 is a safer bet if you intend to either run some of the more demanding games like BF3 that can use 3-5 cores or have stuff running in the background while gaming.
I would personally pick i5 since I always have tons of stuff running in background even while gaming.
for what its worth:
go for the 3450 and a B75 motherboard. the "B" chipsets are usually $10 cheaper at the cost of one 6Gbs sata port and no ISRT (where you use an SSD for a cache drive). the price difference may make the ivy bridge chip doable.
If youhad let us know your budget and the parts you wanted maybe we could have suggested certian parts so that you could get the best cpu for what you want to do.
With gaming the video card plays a bigger roll then the cpu and will give you more fps depending on what you get for a card.