I'll let you know i'm typing this with an i3 4370 so there is going to be some bias, but i'm not going to mislead you.
The i3 4130T is going to pretty much be hitting that 2.9GHz all the time. The i5 and the i7s have Turbo Boost, but since Intel states that their clock speeds can go"up to" 3GHz or whatever, that suggests that the actual base clock is much lower. It will probably be around 2.5Ghz on the base clock and that "up to" speed is for a single core only.
It doesn't really make sense to get anything but the i3 4130T.
the base clock is actually 2GHz and the TDP 35W for that i5, not very encouraging indeed and more expensive,
but still, without 100% load it should run closer to 3GHz than 2GHz while gaming, and perform overall a little bit better for ST and MT.
considering the GPU is just a 750 TI I think the i3 is fine.