When choosing a suction/air pressure vibrator, there are several factors to consider to ensure that you get a toy that meets your needs and preferences:

1. Power and intensity: Consider how powerful you want the toy to be, and look for models with adjustable suction and intensity settings so that you can customize the experience to your liking. 

2. Size and shape: Choose a size and shape that fits your body and feels comfortable to use. Many suction/air pressure vibrators are designed to be compact and discreet, making them easy to use and store. 

3. Materials: Look for toys made from body-safe materials, such as medical-grade silicone or ABS plastic. These materials are non-porous and easy to clean, which can help prevent the buildup of bacteria. 

4. Battery life and charging: Check how long the toy can run on a single charge, and whether it has a rechargeable battery or requires disposable batteries. 

5. Noise level: Some suction/air pressure vibrators can be quite loud, which may be a concern if you need to be discreet. Look for models with a low noise level if this is a concern. 

6. Price: Consider your budget when choosing a suction/air pressure vibrator, as prices can vary widely. Keep in mind that a higher price tag doesn't necessarily guarantee a better toy, but it may indicate higher quality materials and better features.

As with any sex toy, it's important to choose a suction/air pressure vibrator that is made from body-safe materials, and to use it safely and according to the manufacturer's instructions. It's also important to communicate with your partner and explore your own body to figure out what works best for you.