The title of Marquess/Marquis in the English/British peerage has only symbolic connection to the title's antecedents of border / "marcher" lords on the Continent or in England and Wales.

The actual use of Marquess in the peerage was to be a title conspicuously higher and more rare than that of Earl, but not dilute the rank of Duke which was (in general) reserved to royalty and public servants of extremely great and unusual distinction. In general, someone who had particularly distinguished himself while already an earl might hope for elevation to the marquessate.

As with all other peerage titles, it was never associated with any particular (or indeed, any at all) grants of land for private ownership, to say the of bestowal of feudal or governance rights over a territory. Remember that England and then Britain were from the reign of William the Conqueror onward, subject to minor exceptions unitary states, governed by the King's ministers and sheriffs with greater or lesser cooperation of Parliament. The power of a landed peer over his lands wasn't as a ruler but as a private owner. Those powers could be quite considerable of course, but they were artifacts of ownership and not noble title.

In addition to higher formal social rank, Marquesses differed (and differ) from Earls insofar as they are entitled to the prefix "Most Honourable" *vs. "Right Honourable"), if they happen simultaneusly to hold an Earldom with a different title their oldest son can be known as "Earl X" (as opposed to an Earl's oldest son being able to be known as no more than "Viscount X") and their younger sons are entitled to the title of "Lord" (vs. "Honourable"). But these were not and are not really of much consequence in the second and subsequent generation. Someone who inherited a marquessate had in reality the status among peers afforded to him by his wealth and talent.