Determining the best cab or taxi in Haridwar can depend on various factors such as reliability, safety, comfort, affordability, and customer service. However, based on reputation and popularity, here are a few options you might consider:

1. **Haridwar Taxi Services**: This is a well-known taxi service in Haridwar offering a range of vehicles including standard and luxury cars. They are known for their punctuality, professional drivers, and competitive pricing.

2. **Haridwar Car Rentals**: Another reputable option, Haridwar Car Rentals, provides reliable taxi services with a variety of vehicle options to choose from. They offer both local and outstation travel services.

3. **Ola and Uber**: Ride-sharing platforms like Ola and Uber operate in Haridwar and offer convenient taxi services through their mobile apps. While they may not specifically offer luxury services, they provide a convenient and cost-effective option for local transportation.

4. **Local Recommendations**: Asking locals or your accommodation provider for recommendations can often lead you to reliable and trustworthy taxi services. They may be able to suggest services that cater to specific needs or preferences.

5. **Online Booking Platforms**: You can also explore online booking platforms such as MakeMyTrip, Cleartrip, or Goibibo, which often list various taxi services in Haridwar. These platforms allow you to compare prices, read reviews, and book taxis according to your requirements.

Before booking any taxi service, it's advisable to check customer reviews, inquire about rates and any additional charges, and confirm the availability of the type of vehicle you require. Additionally, ensure that the taxi service you choose prioritizes safety and adheres to necessary regulations.