As per the American nomenclature, the only practical difference between SS316/SS304 and SS316L/SS304L is the carbon content.
The carbon content is 0.08% maximum for 304 and 316 and 0.030% maximum for the 304L and 316L types. All other element ranges are essentially the same (nickel range for 304 is 8.00-10.50% and for 304L, 8.00-12.00%).
On the European side, there are two variants of the 304L type, 1.4306 and 1.4307. The 1.4307 is the variant most commonly offered, outside Germany. The 1.4301 (304) and 1.4307 (304L) have carbon ranges of 0.07% maximum and 0.030% maximum, respectively. The chromium and nickel ranges are similar, nickel for both grades having an 8% minimum. 1.4306 is essentially a German grade and has 10% minimum Ni. This reduces the ferrite content of the steel and has found to be necessary for some chemical processes.
The European grades for the 316 and 316L types, 1.4401 and 1.4404, match on all elements with carbon ranges of 0.07% maximum for 1.4401 and 0.030% maximum for 1.4404. There are also high Mo versions (2.5% minimum Ni) of 316 and 316L in the EN system, 1.4436 and 1.4432 respectively. Furthermore, there is also a grade 1.4435 which is both high in Mo (2.5% minimum) and in Ni (12.5% minimum).