I do not agree with those who are saying that the SemiApo is rubbish, the results that can be obtained with this filter actually depend on the subject. I made a test on several Baader filters (it can be read here, sorry it is not in English) and I found the SemiApo very effective in observing, for example, Jupiter as it does not sacrifice blue details while the 495 LP wash them out almost completely. With large and fast achromats with lot of CA the 495 may be preferable but with a well corrected achromat the view through the SemiApo is definitevely more pleasant and contrast is very good. With these instruments there is no need to paint the Moon in yellow.
I would not say the Semi-APO filter is rubbish, but I think for people that haven't tried these filters the name "semi-apo" is misleading and result in people buying the semi-apo filter when another filter choice might be more appropriate. I have compared the #8 light yellow, Fringe Killer, #12 deep yellow, and 495 Longpass directly and at an earlier time tried the semi-apo filter.
For a long time I had the Baader Fringe Killer mounted permanently on my star diagonal. With my Vixen 140NA refractor the Fringe Killer removed ~50-60% of the visible CA. With a 107mm aperture mask I was able to get lunar views that were essentially CA free. Then after reading debates about the various filters on this forum I decided to do a direct comparison of the 4 filters listed above.
Keep in mind that the semi-apo filter is the Fringe Killer (which is identical in performance to a #8 light yellow filter) combined with the Baader M&SG filter. So the semi-apo does no better at removing CA than the FK: about 50-60%. All it does is restore color neutrality --- by removing additional light from the spectrum that is actually focused by the achromat. This is readily seen if you look at the transmission curves on the Agenaastro website. So maybe the semi-apo is the filter a person will prefer, but it should not be assumed that because it is more color neutral than the #8 and FK and because it has the "-apo" in the name that it is the best option. As you point out - it will depend upon observing targets ... and IMO also the scope.
The advantage the 495 Longpass filter has over all the others for certain observing goals is that it offers complete removal of purple CA. I was very happy with the FK for a long time, but when I compared the FK to the 495 Longpass the positive effects of the filtration was taken to a higher level. With the FK I was able to push my Vixen 140 to ~160x for bright globs and ~200-225x on the Moon. With the 495 Longpass I have pushed the Vixen 140 to 200x on bright globs and over 300x on the Moon. Views are sharper and cleaner when I use the 495 LP than with the FK. There is a mild amount of additional dimming but it is made up for by the increased ability to detect fine details and faint stars - and I can use my Vixen 140mm refractor at full aperture instead of using the 107mm aperture mask.
These days I recommend the #8 light yellow over the FK because it is just as effective. For 100mm and smaller achromats the #8 light yellow should be sufficient. For 127mm and larger achromats the 495 LP is the way to go in my opinion.
The only issue is whether or not you can deal with the color shift of the 495 LP - which is only seen on the Moon, planets, and bright stars. But isn't that what color filters are for anyway - to enhance details on the Moon and planets? Use #56 for this, #80A for that, #15 or 21 for ... and so on. In comparison to the unfiltered view you get with an achromat the yellow CA free view with the 495 LP is much preferable to me. If it is not satisfactory to an individual then that person should go with the semi-apo filter or just get an APO refractor.