I owned an L-358 and I now own an L-758DR. Custom profiling is attractive but far from necessary. I'm not saying it doesn't work but think about it.... look at how long photographers have been doing just fine, nailing exposures with a good quality light meter and they didn't have profiling of any kind. I've done A LOT of experimenting with profiling, both with Canon and Nikon and have always concluded that it's cool but far from necessary and not something to drive yourself nuts over. It does not take the place of good metering technique, which is too often lacking.
Other than profiling you have to look at some other features that differentiate the 2 meters. The L-358 will not transmit to and trigger a Pocket Wizard without the $50 option. The L-758DR has the module built-in.
Next, if you plan on doing critical spot metering the L-358 will only give you a 54 degree angle of view for reflective metering and there's a fairly expensive optional accessory you can add to do spot metering but it's cumbersome and can't be put in the case with it mounted. The L-758DR not only has a built in 1 degree spot meter but it also has a very cool viewfinder with an LED display that makes it very easy to use the spot metering function.
There are other cool features in the L-758DR but the gist of it is that if you are looking at those 2 features and deem them as important then it doesn't make sense to get an L-358 and buy the optional accessories because at that point you're already approaching the cost of the L-758DR.
In terms of measuring and metering light (which is the point of the light meter), either will do the job and neither will do it better.