what makes a bass feel fast?

[chickenjames]

so I am now the proud owner of two 4 string basses - EBMM StingRay 4 and a Sire Marcus Miller V7 J bass.

I _think_ they're both set up fairly similarly - the MM is as it came from Thomann and I've done the EBMM myself.
They both have d'Addario Chromes (flats) and the action seems to measure about the same on them both. I set the truss rod on the Ray so that I could wind the saddles a long way down on all the strings without buzzing, which feels right now.

But - and here's the fun bit - they feel completely different. Even before you plug them in or listen at all, they're worlds apart.

The Ray feels super smooth, and the MM is beautifully clanky.
If you pick the MM up by the top of the neck it feels extremely thin compared to the Ray, and it's just, well, quicker. It feels easier to get more notes in , if you know what I mean.
That's not to say that there's anything I dislike about the Ray, just that the MM feels somehow turbo-charged.
The touch sensitivity on the Ray is noticeably better though - it's much easier to vary tone and articulation (staccato vs legato etc) with my fingers.
I know nothing at all about nut width, neck profile and string spacing so I'd be very interested to see if anyone could explain my experiences by reference to these things!

To be clear, I love both of these basses and I'm expecting to use the two of them fairly equally through a set. (Which BTW says quite a lot about the value for money in the MM, considering that it set me back £300 and the MM was nearer £1000, new - it's the special edition 2EQ plain version with a gig bag).

comments welcome, thanks