The main difference between them is a BEng is 3 years whereas MEng is 4 years and covers the academic requirement for becoming chartered. At Lancaster University, you can apply as a BEng and then if your grades are good you can be invited to switch to the MEng at the end of second year. Or if you start as a MEng and then realise you don't want/need to do a fourth year then you can switch to the BEng.
If you are thinking of swapping career path to finance or tech, engineering has great transferable skills but you could also do a postgraduate course in something different after an engineering undergraduate degree. MEng looks good to future engineering employers as it shows you have committed an extra year, have a higher level of engineering knowledge and at Lancaster we do a year long group project in fourth year which is great to talk about at interviews. Not everyone wants to stay at university for a fourth year and if you do a year in industry then thats also an extra year, but if you want to get charted in the future than you need to demonstrate further learning such as a MEng or another postgraduate level degree. Ultimately, it depends on what you are interested in, what career paths you are considering and how many years you want to do engineering at university. I hope that helps, let me know if you have any other questions : )
-Izzy (Started as a BEng but switched to MEng and is a current fourth year)
(Lancaster University Engineering Student Ambassador)