Short answer: It depends!
As a day trip, I’d like to make something very clear that all other guide books lie about: They all claim that Malacca is a 1.5 – 2h bus ride away from Kuala Lumpur. This is SO not true!
What they are referring to is the ideal bus time from TBS, the bus terminal south of KL to the bus terminal north of Malacca.
To get to TBS from the center is nearly another hour (taking 2 different trains), getting from Malacca’s bus terminal to, let’s say, Jonker Street takes another 30 minutes (Initially we wanted to take the local bus, but then decided on Grab taxi)
For us today, door-to-door, it took 4h to get to the center of Mallaca and 5h on the way back, thanks to traffic!
Glad we got back at all! Once we arrived at the bus terminal, we followed guide books’ recommendations to get our return tickets right away, only to be told from the first 5 bus operators that all busses after 2PM are already SOLD OUT!
In panic we started looking for hotel rooms, but we then found a ticket counter called ‘Catch that Bus’, which I think might be a broker for smaller bus companies (?), and they still had tickets on the 6PM bus, which was a bit later than we wanted, but what could we do.
In the end we arrived back home after 10PM, after everything but 7/11 had closed and our dinner thus was a mix of cup noodles, onigiri and chocolate.
Now, coming back to the initial question: Is all the above in any way proportional for what you are ‘getting’ from a trip to Malacca? Let’s see, we got a really nice bowl of laksa for lunch, and there was a very informative museum built into an old tall mast ship replica which I hear was cool (I skipped out on that).
There are a bunch of old relicts / ruins from the port heydays. And some of the walks along the river / the streets reminded us a bit of Hoi An.
Thanks to land reclamation, Malacca is not even that close to the sea anymore, besides the canal it does not feel much like a port city.
And then there are the touristy things, shops with the usual souvenir trash, but probably the most ridiculous thing I have ever seen are the bicycle rickshaws, decorated with whatever fairgrounds’ shooting booth rejects they could find, playing the most annoying techo / EDM (not even sure what you would call that music) trash AT FULL BLAST! Please click here for a great example I found on Youtube.
For sure, this is something rather ‘unique’ … but not in a good way.
Having said all that (and probably missing a few points), I cannot recommend Malacca as a day trip from KL.
What I could imagine instead is either as a stop over on the way to Singapore (another 3h down the same highway), or (maybe) stay a few nights in season / on weekends, when, as far as I heard, the place is hopping and there seems to be some kind of nightlife going on.
I DO recommend very much that IF you go there to get the laksa at Jonker 88, and some cendol afterwards.
And for afternoon coffee go to Calanthe Art Café (also known as ’13 states coffees’), that was very nice.