there are very fine differences between SE k750 and w700
focus
k750 has auto focus (AF). and w700 has fixed focus (FF) lense.
fixed focus means, everything from a minimum distance to infinity is in focus. for w700 the minimum distance is something like 4.8cm.... (check on the camera lense)
auto focusing in k750 takes a second or more. till the rectangle becomes green.
where as for fixed focus u can just press the button... no need to focus. it is truly 'aim n shoot'.
but, with focusing (AF) you can do some tricks after experience. especially with macro mode. and u can get appriciable results.
for normal user fixed focus is best.
there are few more differences in camera
zoom
in w700 you can not zoom whilst in higher resolution (1632x1224)... a big minus! but i think thats the limitation due to fixed focus...
also, u can zoom 2x for the picture size 640x480
i havn't checked it. but, then the specified 4x zoom must be for the smallest size 160x120
flash
here w700 has a winning point
in k750 images taken with flash turns yellowish in shade
but w700 renders colors correctly with flash
camera cover
again w700 has plus point with the cover
the sliding camera cover of k750 damages photo sensor of camera
it affects physical stability of mobile when kept on plain surface
also, the metal coating of camera cover normally sheds off after overuse
w700 has a button which rotates a small lid... i feel that is better
some other differences to notice
sound quality
this is not my personal opinion but, the sound quality seems to be less than w800 and almost equal to k750
battery
w700 uses lithium ion battery (Li-Ion)
whereas, k750 uses lithium polymer battery (Li-Po)
they both claim to be having same talktime... but the batteries are different
if u guessed it, the lithium ion are cheaper!
memory card
considering the price, u can easily replace ur memory card for cheaper rates. so this can not be a point of difference here.
my friend got 1gb in exchange with 256mb for the difference of rs. 900.
but, k750 supports cards upto 2gb. whereas, w700 has 4gb cards available & might go up to 8gb. more than enough space for music! so w700 has a big plus here.
price
there is hardly a price difference of rs. 1000
which should not be a major issue
and after all the w700 has software features of w-series... for walkman
or you can also try the options by suave_guy
but flashing is not that easy... so be careful
verdict
if you are music addict, choose w700
if you are keen in camera, avoid w700