Bicycle Mechanics - Shimano flat bar shifter questions.

Ok so my family/commuter bike is a flat bar Marin Mill valley and I am not all that impressed with the Shimano R-440 shifters. Can I use the MTB groups for shifters? Would LX be an upgrade to the 440 or should I just go for the XT. For reference this is a 9 speed with a Tiagra rear derailluer (also probably going to upgrade the derailluer) and a Tiagra 12-25 road cassette and Tiagra triple (52/42/30) which I think I want to change to a compact double. I have heard the gear spacing is the same from MTB to road cassettes so I assume the MTB shifters will work fine but I wanted to make sure I am not missing some key point.

Ok so my family/commuter bike is a flat bar Marin Mill valley and I am not all that impressed with the Shimano R-440 shifters. Can I use the MTB groups for shifters? Would LX be an upgrade to the 440 or should I just go for the XT. For reference this is a 9 speed with a Tiagra rear derailluer (also probably going to upgrade the derailluer) and a Tiagra 12-25 road cassette and Tiagra triple (52/42/30) which I think I want to change to a compact double. I have heard the gear spacing is the same from MTB to road cassettes so I assume the MTB shifters will work fine but I wanted to make sure I am not missing some key point.
Mtb rear stuff interchanges. You might have issues with mtb shifters and the flat bar FD.

Mtb rear stuff interchanges. You might have issues with mtb shifters and the flat bar FD.

How so? i.e. what issues?

I could keep the 440 left shifter and just change the right I suppose. Thinking about it I almost with this bike had down tube shifter bosses as I would just go to a downtube shifter for the front....maybe I can get an old friction shifter from a MTB for the front.

Mtb rear stuff interchanges. You might have issues with mtb shifters and the flat bar FD.

My wife has a Specialized Crossroads Pro that came stock with Rapid Fire shifters and a Tiagra front derailleur. It works just fine. I have a similar combination on my daughter and son-in-law's tandem too. For some reason that I don't fully understand, I don't think that it works so well the other way (STI shifters with MB front derailleur).

You can use the Lx or Xt shifters with any 9 speed read dr. But the front you need the Shimano R440 front. It has the proper throw ratio to work with the Road triple. As you have a Marin Mill Valley, you might already have the proper front dr. Most of last year I ran XT shifters the R440 ftonr dr and an XT rear on a Sram 9 12 -32 9 speed on my commuter bike ( Converted roade frame) with a flat bar and a cross triple 48/38/30. I had no problems at all, it was a pleaseure to ride.