Many say the 75-300 isn't a very good lens but I disagree. I own one and have excellent results with mine. I also own the t3i and it's an excellent camera for both stills and video... now that I have it I won't go to any other... why? The t3i has everything I want in a camera.
For photography I think both are almost the same.
But in the video subjet, the T3i is way better. In the the video mode you can control ISO, Speed, Aperture... In the T3 you can't just auto mode.
If you you want to save some money and just take pictures and video in auto mode. Go for the T3... If money isnt a issue go for the t3i for sure.
It depends bro. 18-55 is a wide angle so it's good on land scape and close ups. It's a decent lens. The 18-135 is also solid but if you want a zoom I suggest u get one specifically made for zoom I shoot professional motocross and I use the canon 70-200 f4l that lens is beauty it makes pics look insane. It's pricy tho. I do suggest the 18-55 and later purchasing a 70-200 whether it my be an l serious or not. Hope it helps.
I would tend to recommend not relying on the internal flash for this kind of thing but instead to consider an external flash like the Canon Speedlite 430EX II. In poor light, the internal flash uses bright pulses of light to provide enough light for the focusing system to work properly but these light pulses can be extremely distracting for your subject. The external flash uses a much less intrusive red focusing beam. Light from the 430EX can also be bounced from a white wall or ceiling in order to create a much softer and much more flattering quality of light. Also, the 430EX recharges much faster for the next shot, has greater range and doesn't eat up your camera's batteries.