Is Malaysian Borneo worth adding for wildlife?
Yes, if wildlife is a main reason for the trip. Borneo can be the part of Malaysia that changes the whole journey, but flights, lodges, guides, weather and park access need more planning than a city-and-food route.
Answer
Malaysian Borneo is worth adding when wildlife or rainforest is not just a nice extra but a core desire. Sepilok, river areas, caves, rainforest lodges and mountain edges can give Malaysia a completely different weight from KL, Penang and island beaches. The trade-off is planning. Borneo usually asks for domestic flights, booked accommodation or tours, and more thought about timing and ethics. A casual two-night wildlife detour often undersells the region and overworks the traveller. Give Borneo proper days and it can be the memory that defines Malaysia. Add it lazily and it becomes a costly logistics loop.