I was wondering if there are any noticable performance differences between the two types of motherboards? ITX can run some pretty decent PROCESSORS but does it size really affect its performance?The physical size does not affect performance. In fact, performance differences between motherboards (if all other hardware is the same) are not typical, perhaps a new memory controller may GIVE a better benchmark score but that's about it.
Instead, look at the CPU socket and chipset, which determine amongst other THINGS what processors you can use, also look at the type and number of expansion slots.
A Mini-ITX board supporting only single core Atom processors with 1 RAM slot and a PCI slot is not a basis for a high performance machine, however other ITX boards support other hardware.
The main advantage to ITX is its small size, leading to its use in small form factor machines such as HTPCs. ATX boards are more mainstream and due to the larger size generally have more expansion slots and therefore flexibility.
Is there anything specific you were wondering? The above is just general information which may not answer your specific question, if you have one.nothing in specific really
was just browsing though newegg and noticed a ITX that supported core 2 duo, core 2 EXTREME, and core 2 quad.
the board also had onboard nVidia 9300 GPU AND! PCIe x16 lol
i was dumbfounded that something so small could handle such components
my next build might just be a itx.
heres the link if anyone is curious http://www.newegg.com/Product/Product.aspx?Item=N82E16813500022

ONE MORE THING!
do ITX mobos use standard ATX PSUs?Some of the higher end boards, especially the ION platform, are designed for higher performance small PCs, yes. That Zotac board is a good example.
Also, most ITX boards do use ATX PSUs as far as I am aware, certainly Intel's Fly Creek boards and that Zotac board use standard connectors.