Metatrader 4 and Metatrader 5 have a number of crucial differences. First, they are built around different programming languages. The name of the programs drops a hint at the programming languages used in the creation of the trading platforms. So, these are respectively MQL4 and MQL5.
Metatrader 5 is a 64-bit program released in the year 2010, while Metatrader 4 was created for 32-bit computers in the year 2002. As Metatrader 5 is 64 bit program, it uses computer resources like cpu, ram, etc more efficiently than Metatrader 4 which means it can load and run any kind of resource hungry indicators a lot more easily than Metatrader 4.
MT4 was specifically built for forex traders, whereas MT5 was designed to provide traders with access to CFDs, stocks and futures.
Metatrader 5 has more order types compared to Metatrader 4.
When it comes to technical analysis, Metatrader 5 offers more. In contrast to Metatrader 4 that offers 30 technical indicators and 31 graphical objects and 9 timeframes, Metatrader 5 comes with 38 default technical indicators, 44 graphical objects, not to mention 21 different timeframes. Both platforms support customized technical indicators.
One can generate tick charts, volume charts, renko charts, range bar charts, etc easily using a chart generator indicator/script on both Metatrader 5 and Metatrader 4 but even if you do use a chart generator to generate volume charts or renko charts or range bar charts on Metatrader 5 platform, Metatrader 5 platform does not allow trading from custom charts. You can bypass the restriction, but that requires a special trading utility such as a trading panel or EA. The utility will translate the custom symbol name to the tradable symbol and mirror the entries plus stops on the custom symbol. Metatrader 4 platform does not have any kind of restriction related to trading from custom charts.
Metatrader 5 does not offer offline charts compared to Metatrader 4 which is why it is harder to program an add on Simulator for Metatrader 5 platform. This is the reason why only Metatrader 4 has Soft4fx and Sphere Tester Forex add on Simulators and Metatrader 5 platform does not.