"It's a no-brainer, mainly because of value," says McGettigan, aka FPL General, on the latest FPL Show.
"He's a big drop from Kane's price value so you have all that extra cash to play with."
More than half a million managers have so far bought Rashford and the Manchester United forward could break the FPL record this season for the most transfers in for a single Gameweek.
This is held by Theo Walcott (£6.1m), who was brought in by more than 772,000 managers for Gameweek 4.
McGettigan says the forward's form under United caretaker manager Ole Gunnar Solskjaer is another reason why so many have made, and should make, the switch.
"He’s got four [goals] in his last five [matches]," says McGettigan. "And the fixtures are great for United so I expect him to keep firing."