i'm not the biggest honda fan (though i love imports) just for the reason that they are everywhere.
the lude's interior is FAR FAR FAR and away superior in layout and material quality to that of the si. my bro has a 98 lude, and a friend of mine has an si. i drive both somewhat frequently, and i prefer driving the lude when i'm busting through the twisties around here. it feels nicer, but is slightly less agile in the initial turn in (probably cause of the weight).
both got nice reving engines, and are silky smooth. don't let the fact that the lude is discontinued daunt your decision. the '99 si isn't in production either, as they changed to a new body. just cause the model is still out doens't mean crap about parts. both cars respond well to simple modifications.
bottom line, if you are just looking for a fly ride thats fun and quick, get the lude. if you are looking to build something to auto-x a lot, get the si, as it has more potential in auto-x than the lude. the lude is still most definately a capable auto-x car, but its too heavy. the si will most likely last a while longer (40k miles is quite a bit) but this also depends on how well the engines were broken in.