Obviously in some situations there might be good operational reasons why you'd need to join circuit on the base or final legs. But as a general practice, is it safe or advisable to do either?
Further to your original post, a lot of higher performance aircraft, especially turboprops and airline flights for example, do favour straight in approaches. They generally offer more efficiency and less low level manoevering with the opportunity to establish a nice 'stabilised' approach from some distance out. They can be conducted very safely and usually such aircraft are monitoring and making calls on the CTAF from 30nm or more out. When communicating about INTENTIONS it keeps everyone informed and the procedure can be carried out safely so long as all parties are involved. By all means, don't be afraid to speak up and talk to these guys on the radio if you think you will be in the circuit around the same time as them! Even though they might make a call at 30nm they can be in the circuit in well under 10 minutes and that has caught many people by surprise.
An important reminder here for both light GA pilots and heavy metal pilots. Refer Jepps ATC pg 715 (section 6.2.1.8) and CAAP 166-2(0) section 11.2
So as not to impede commercial aviation, pilots flying
recreational or sport aircraft for their own enjoyment, or pilots
flying GA aircraft for their own leisure, should consider giving way
to aircraft being used for ‘commerce’ provided that the
inconvenience to their own operation is not great and it can be done
safely. Operators of commercial flights should never expect a give
way offer to be assumed or automatic. Any offer to give way must
be explicit and its acceptance acknowledged.
For someone such as yourself, a circuit join from overhead is hard to beat and gives you time and space to fit in with traffic as well as the best look at the windsock prior to landing. At the PPL stage, most good flying schools would encourage you to primarily follow this principle but don't forget (as you have now well experienced!) that there are others out there joining at other points in the circuit.