I have the RF 24-240 lens for my EOS RP. I also have EF 24-105 f/4L mk1 lens. I don't have the RF 24-105 f/4L lens.
The RF 24-240 lens has several quirks you need to know:
- Lack of weather sealing
- Lens hood needs to be bought separately
- Manual focus switch is missing and you need to set it in the camera menu
- The focus/control rings are combined into one
- The chromatic aberration prior to correction is terrible. So, you really need the lens profile. After correction, the CA doesn't annoy me. Open source software currently lacks the lens profile, so you really need to use Canon DPP.
- In low light (read: indoors), at long focal lengths, the focusing is not suitable for quickly moving targets so this is not a pet photography lens at 240mm if your pet moves quickly. It's also not a sports lens. Well, you should already know that from the small aperture, especially at long end.
- At long focal lengths, there is slight lack of sharpness in corners.
- At short focal lengths (24mm), it's actually a 20mm lens with huge geometric distortion, and black corners, and the lens profile in the camera firmware and/or RAW software applies corrections to make it 24mm, correcting the geometric distortion, and removing the black corners.
Summary: don't shoot in the rain, don't shoot sports/action, don't expect good corner sharpness at long focal lengths, and you really need to use Canon DPP and new firmware in EOS RP.
However, there's several good things about the RF 24-240:
- The image stabilization. I mean, the image stabilization! It's wonderful! I have never seen such good image stabilization anywhere. You can handhold near 1 s shutter speed, and you really do get the full 5 advertised stops. So, if you are photographing slowly moving targets in low light, this is the lens to get. The good IS for non-moving targets is so good that you don't care about the slow aperture in low light.
- The range of focal lengths is good, and center sharpness at 240mm is acceptable, so the lens is fun to use. If 240mm is not enough, you can zoom the center digitally. It's not a birding lens but then you should know that already.
- It's a all-in-one lens. You don't need to be continuously switching lenses. For travel, that would be the key, but I still like the lens even though I'm not a traveller.
If you decide to get 24-105 instead, I would consider some used EF 24-105 L series lens too. They lack the high speed display option but then again that's more useful for sports and birding, and the EF 24-105 lens ain't a sports or birding lens. Also note that some EF 24-105 lenses have zoom creep when old.
For EOS RP, I find the RF 24-240 the optimal lens. For a hypothetical high-megapixel EOS R series camera (not announced yet), the RF 24-105 would be better.
Neither lens is an astro lens. For astro, use the 50mm f/1.8 if you don't want to capture wide milky way photos and a narrower photo is enough, or preferably find a wider lens.
I like to take pictures while traveling, at home I enjoy macro photography and Astro photography
Get the RF 24-240 because you mentioned the magic keyword travel!
Use the 50mm f/1.8 for astro now and consider a wider fast astro prime later. For macro, you need to find something acceptable as RF 24-240 ain't a macro lens. The RF 35mm macro has only 0.5x magnification and costs a lot for a 35mm lens. You could consider if you can find some used full frame macro lens for EF mount.
Edit: You could of course consider the RF 35mm f/1.8 lens with 0.5x magnification for both astro and macro. For astro, you should prefer something like fast 24mm prime, and for macro, you should prefer something like 1x magnification, but if you can live with 35mm for astro and 0.5x magnification for macro, the 35mm lens could be it.