Like you I am very keen on planetary imaging. I got started with an 8SE SCT, graduated to a C11, and now own a C14Edge HD (the Edge version of a C14 is not strictly necessary for planetary, but it does have a lockable primary mirror which improves the stability of your collimation). As Callum says above, SCTs tend to be the default option for planetary, and they are excellent for the purpose. From my observations of the work of others, a 9.25″ SCT is a very good compromise between power and portability.
But during my apprenticeship as an imager, I was living part of the year in Strasbourg, imaging from my apartment kitchen window. There, I used a Celestron guided Maksutov-Cassegrain (a 127SLT). This I found to be an excellent little scope for planetary and lunar:
1. It is very transportable – I used to take it for star nights in Saverne in the Vosges mountains;
2. It is already at f15 so barely a need for a barlow if you use a camera with pixels around 2.9 microns;
3. As a Mak Cass, there is essentially no need to collimate, whereas with an SCT you need to be very careful to collimate to a very fine degree (i.e. using the Airy disc), especially after transporting the scope;
4. The alignment procedure for the Celestron 127SLT includes “solar system alignment”, which means you can just point it at the planet and align – you don’t need two or three alignment stars, whcih can be an issue in an urban setting (certainly in my apartment looking out over Strasbourg!). The tracking is then sufficiently good for planetary imaging (especially if you check that the OTA is well balanced on the mount, if necessary adding a small counterweight to balance the imaging train).
So, go with an SCT if you want to be really serious; or try a small Mak Cass just to dip your toe in the water.
BTW there are some excellent FAQs on planetary imaging here: