mech ones are a bit of a pain in that they are a bit hard to get at
can leak oil if worn out or yukky surfaces on block & gaskets & spacers etc
can leak fuel if torn or split diaphram inside it, so fuel can leak outside , or leak into the engine diluting your oil with lots of fuel
elecy pumps are many different types avaliable, be aware that the cheap ones are just that
but then even some top quality ones are not so top quality
BUt, youll have to run a new wire through from your fuel block all the way back to the rear of the car, under & to the left hand side of rear subframe (where we mount the pumps & where the original "S" ones were mounted) so can be a bit of a muck around either way
in my opinion it`s much of a much-ness which one you choose for road use
but for racing i always use elecy type
edit--> Oh & before i forget,,, be aware that some of the later designed mechanical ones run their exit pipe very close to & run around behind the exhaust pipe,,, not my kind of idea (some bright spark thought that up) pardon the pun
but can (& often does) cause some vapour locks in the fuel lines on hot summer days stuck in traffic
i have more "fors & againsts" if you like

sorry,,, just replace the one you have as it may be easier for you
or pay the extra & get an elecy one fitted & wired in