There are many different mobility scooters on the market. You will have to select from numerous different Brands, such as Shoprider, Pride, Heartway, Drive, Kymco, Solax and more. Each of these brands has some different models, so the choices are vast.
In this review I will focus on reviewing your everyday type scooter also know as Medium Gophers, so omitting smaller travel, portable and large heavy duty & all terrain mobility-scooters.

I have chosen the top sellers from the most popular brands in the same price range and will be comparing them on the below factors
-Weight capacity
-Travel Range
-Suspension and Seat
-Top Speed
-Comfort and Safety Features
-Climbing Angle

The Products for comparison that I have chosen are:
Drive - Viper

Heartway - Mirage
 

Kymco - Agility
 

Monarch - Volta
 

Shoprider - Rocky 4

Weight Capacity
The weight capacity of a scooter is more than just a maximum carrying ability, but also a great indication of the size and power of your machine. When doing my research, I found that some scooter brands advertise their max user weight based on flat ground measures, which dramatically decreases when there are slopes. To standardise the findings, I have used an average of the lowest slope of 6'. That's why it is always advisable to choose a Scooter which allows 10kg-15kg more weight than your actual weight. Out of our 5 Test Gophers, they ranked as below
Highest carrying ability with 165kg is the Kymco Agility Scooter.
The Viper, Volta and Rocky 4 all came in around 150kg or above.
The lowest weight capacity is offered by the Heartway Mirage with 135kg

Travel Range
When looking at a trip range, try and think about where you are planning to ride your scooter and use Google maps to determine the approximate return trip distance. It is important to note that as your batteries get older, the range that you can ride your mobility scooter on a single charge will start to get shorter.
The Agility, Rocky and all came in at 40km, while the Mirage sit's on 30km and the Volta on 25km.

Suspension and Seat
You want to make sure that your scooter has ample suspension and a supportive seat. While navigating a well-paved footpath or a shopping centre won't require any suspension you will start to feel the difference once you have to navigate a few potholes, kerbs and park paths. Unfortunately, this is an area that makes for hard comparison on paper, as a lot of the scooter manufacturers/resellers won't give much information on the suspension and only write "ample suspension" or "state of the art suspension". My best advice is to test ride the scooter and make sure to take it over some potholes or drains so you can get an indication of how the suspension works.
The seat is also hard to compare as this is a personal preference. All of the scooters in the case study have a tall captain style seat, with adjustability features and swivel seat.

Top Speed
To comply with Australian Standards and regulations the maximum speed of gophers is often adjusted by the seller to 10kph. However, most scooters are capable of faster speeds. All the machines in this comparison have a top speed of approximately 13kph.

Comfort and safety features
Similar to the seat, all of these scooters offer Delta handlebars for a comfortable grip and an adjustable tiller.
Mirrors
Only the Agility, Mirage and Viper come with side mirrors as a standard.
Dash
All of the scooters except for the Kymco Agility feature an analogue dash. The Agility has a waterproof LCD display which allows for comprehensive information such as time, trip meter and odometer readings.
Drink holders and tiller pockets
The Agility, Mirage and Volta all allow for some room on the tiller to store valuables and a bottle. Unfortunately, neither the Rocky nor the Viper has allowed for this added convenience.
Lights
All these scooters offer a full lighting package, including front, rear and indicators.
Other
The Agility provides a charging socket for a tablet or mobile phone.

Climbing Angle
This is the maximum incline in the road that the scooter can safely handle, without loosing significant power or causes risks due to tipping.
Agility:12'
Rocky: 12' *please note that this will reduce the weight capacity of the scooter to 100kg
Mirage: 10'
Viper: 8.'
Volta: no information supplied

Overal Findings

1. Kymco Agility - This scooter came in first or second place in all the factors and offers additional features such as LCD Display, mobile phone charger
2. Viper & Mirage - Both mobility-scooters are very similar. I would recommend making your decission on the drive experience, look and feel of the product.
3. Rocky4 & Volta - I have ranked these two scooters to be the least desirable of the bunch due to numerous reasons. Availability of information - I have spent a lot of time to try and find information and specifications on these scooters. Unfortunately, I still wasn't able to find all the required information and some information was not consistent.