What are the key considerations when choosing a tablet or smartphone to use with an indoor trainer, and how can riders maximize their training experience by leveraging the unique features of each device type? For instance, how do the larger screens of tablets impact the immersive experience of virtual training rides, and are there any drawbacks to using a larger device in terms of portability and convenience? Conversely, what are the advantages of using a smartphone, and how can riders make the most of their devices compact size and touchscreen interface to enhance their indoor training sessions? Are there specific apps or software that are better suited to one device type over the other, and how can riders ensure a seamless and lag-free experience when using their device with an indoor trainer? Additionally, what role do factors such as processor speed, RAM, and storage capacity play in determining the overall performance and responsiveness of a tablet or smartphone when used with an indoor trainer, and are there any minimum specifications that riders should look for when selecting a device for this purpose?