T3i is better at lower ISO levels than Nikon D5100? - 1

And D5100 is better at higher ISO level than T3i. I'm comparing many photos on Flickr from the T3i & D5100 and it seems that the D5100 seems to yield softer photos compared to T3i. I'm confused because many reviews say that the D5100 has a slightly better edge over the T3i in terms of image quality but I find this to be the opposite after comparing hundreds of different photos on Flickr from different photographers using different lenses.

I think the question would have to be how you are comparing them, and are you truly comparing like for like? The only real way to compare such cameras is in the laboratory, and even then your results will also be colored by the optics of the lenses used. With out subjective, blind testing, personal preferences are likely to show though.

Here, DPReview compares the same image between the T3i and D5100
http://www.dpreview.com/...ond5100/19

Its really hard to trust photos online because some of them arepost processed with Photo editing softwares before uploaded.

The D5100 has a tiny bit of edge on lowlight with higher ISO compared to T3i. But that can also
depend on the photographer and the lens used.

Common stereotype is that:
Canon = video quality
Nikon = image quality

All i can say is, you can't go wrong with the T3i.