The best software to buy is one that does what you want it to do. All CAD systems are different although they fit into various categories. Catalogue driven or generic or a combination of both. And software like AutoCAD® that is a 2D line drawing CAD with no libraries branded or generic. It produces technical drawing layouts and was the traditional choice of the bespoke designer until the ability to retain the technical appearance of their plans and produce 3D images was made available through software powered by an AutoCAD® OEM engine together with kitchen cabinet, appliance and accessory catalogues.
The ideal software package might not be affordable now but it might be possible to start with a cut down (light version) and upgrade later. Some packages have a base operating system and have various modules that can be added to tailor the software specifically. One thing is for sure with software is if you buy cheap you buy twice, so establish a list of features that are important to you and not assume that they will all do the same thing. Dig deeper and make sure.
Any of the CAD companies will offer to demonstrate their software to you and it will be with the expectation of selling you their product. There might be a feeling of pressure especially if the sales person is sitting there with you and has travelled some distance. This stands to reason whatever you are looking at buying.
Before you go this far do some research and narrow it down and don't succumb to any pressure. You want to buy not be sold.
One the face of it an excellent idea but it's usually the cheaper software that can be trailed and also software that is weaker on features. The reason being that the less it can do the less to learn. The more capable software will need at least some training so that the software can be evaluated from a point of knowledge instead of being dismissed because the user wrongly assumed it would not do something they wanted it to do.
In my view you should be able to discuss what you need and be shown how to achieve it by a real person who is happy to invest their time in you. Trial version schemes are for companies who are aiming at the masses and something as diverse are kitchen bathroom and bedroom designing should be done with a more personal approach.