Canon has several product ranges.
All "Rebel" bodies are in the "entry" level range. If the Rebel body has an "i" suffix in the model (e.g. T5i) then it's in the upper end of that entry range. If it lacks the "i" suffix (e.g. T5) then it's in the lower end of that entry range.
Canon has a mid-level / prosumer range of camera bodies. All of these bodies have two numeric digits in the model number. E.g. 70D, 60D, 50D, ... all the way to 10D. The 70D is the latest, but they do still market the 60D (even though that model was introduced several years ago.) These are bodies which start to introduce features found in the pro bodies (like a top LCD, a large selection dial on the rear of the body (that all pro bodies have but all Rebel bodies lack). But they ALSO retain some of the entry level features of the Rebel bodies (like "scene" based modes). Canon also adds some build quality features such as some weather-sealed treatment (they are NOT waterproof. Weather-sealed implies that if the camera is splashed, gets some rain on it, etc. that it'll be ok -- although this assumes you are ALSO using a weather-sealed lens and the vast majority of lenses are not weather sealed. Most of Canon's high end "L" series lenses are weather-sealed.
Canon's higher end bodies have just one numeric digit in the model number. E.g. the 7D & 7D II, the 6D, the 5D III, and the 1D X (the 1D X is the flagship body). With the exception of the 6D, these are arguably "pro" level bodies. The 7D bodies are optimized for high-speed shooting (sports/action). The 5D III is a high-end full-frame body. The 1D X is the highest end body, which is full frame, but blazingly fast (faster than the 7D bodies). The 7D II, 5D III, and 1D X all have very advanced focusing systems. These higher end bodies don't bother to include the entry-level features such as "scene" based shooting modes (pros would never bother to use them.)
The 6D is a bit special in that it's actually a full-frame body designed to have a lower entry-price (normally full-frame bodies have price tags of at least $2k for the body only... and often closer to $3k and up). The 6D is about $1800 -- which is cheap for a "full frame" body.
In answer to your question... is the 70D better than the Rebel T5i? Yes, absolutely it is. It's better in pretty much every way. It has a new sensor which is capable of performing "phase detection" type auto-focus directly on the sensor itself and this allows it to do continuous auto-focus during video WITHOUT having to do "focus hunt". It also has a vastly better focus system (19 AF points -- all "cross type", vs. the T5i's 9 "cross-type" points.). It has better body build with weather-sealing. It has a better control layout with more instant-access buttons to get at features you'd change frequently without having to go through menus. It has the rear-dial that Rebel bodies don't have which allows much faster access to controls.