My other thought would be perhaps the stormies would have a little bit more definition and bite with the maple of the 335 rather than my thick bodied all mahogany Gordon Smith which they are currently in.
I think that may be true. If it's not enough, you could go for a subtle (and inexpensive) change by swapping the A2 magnets for A4, that would tighten things up a bit. I think Derek (Fourth Feline) did that with his SM set (albeit in an SG, not a 335).
Hiya Tom , :)
I eventually tried my Stormy Mondays in both the Gibson S.G.
and a 'Tanglewood' 335 copy.
As PhillyQ pointed out, I eventually changed Alnico II magnets for AIV types - as ( especially in the 335 copy ) the bass strings sounded a bit soft and 'blurred' . They make nickel plated strings sound like
pure nickel wound.
Ironically in a Les Paul ( Mahogany with Maple top ) - Even the Alnico II Stormies sounded clearer than in either the wholly Mahogany S.G. - or the Basswood body / Mahogany neck 335 copy.
For the 335, I ultimately got the combination / balance of fat, yet articulately clear highs
and clearly defined bass response, by fitting Mississipi Queens . At the time I specifically wanted a Larry Carlton ( Sapphire Blues Band era ) sound / vibe. As his was 335 is maple and thinner laminates are used, his Gibson '57 classics seemed to do O.K ( although I hear they tend to have quite a 'bite' for Alnico II pickups ).
On balance, considering your needs and my evolution through AII Stormys - AIV Stormys - Mississipi Queens - then eventually putting it's ( no name ceramic ) pickups back in - I would therefore lean towards / agree with Ratrod's suggestion of Riff Raffs. My reasoning being that if upgrading a 335 pickup set, that bass end articulation
may need addressing ( so the bass strings do not get 'lost' and mellowed out in the natural body resonances of a semi-acoustic ).
As far as pickups I have actually owned / experimented with - I would highly recommend the Mississipi Queens, but the Riff Raffs ( I once heard ) will have such a surfeit of 'bite' and clarity, that tone controls and E.Q can be used to 'tame' them if needs be.
The Mississipi Queens are gorgeous in a 335, but are fatter sounding - and being basically a nickel boxed P90 - ( i.e. with the pickup screw heads / pole pieces sitting closer together in the centre ) - the tonal difference between neck and bridge is more subtle ' they
DO sound different, but it's shades of grey - not black and white. I tend to use the middle pickup position almost exclusively, so this was ideal for me .
My caution about the Mules ( which I have only ever used in my Les Paul ) - is not that they would be too aggressive, but quite the contrary, in that the slightly increased mid range 'hump' over the Stormy Mondays - might produce a darker effect in the semi- acoustic format, whereas Mississippi Queens are fat but essentially single coil pickups, so you get a very clear glassy edge on that 'fat' sound if you flip to the bridge pickup and dig in.
So, for the reasons stated, Riff Raffs or Mississipi Queens get my vote for your purposes. :)