don't forget the WaveSurfer series has some limitations in terms of options, compared to WaveRunner's and WavePro's.
In particular am I thinking of the XDEV, XWEB & XMAP options, which can be pretty useful... but those are maybe no longer relevant with the latest software versions... to be checked with LeCroy.
In the past, there was also a limitation in the number of distinct grids that could be displayed, etc...
Now, if you have no need for the RF part, why an MDO ?? (and the MDO3K is no real MDO anyway, as there's no way to correlate time- and frequency data).
An interesting scope that is sometimes offered by Tek at seriously discounted prices (10-12K with full warranty), is the MDO4104C(-SA6). That is a real MDO, with amazing capabilities (see the review by The Signal Path), if the RF part is relevant for you.
But if math is the point, no hesitation... those old PowerPC scopes (MDO3K, 4K) can't compete with a modern Intel CPU !