Choosing a glass or metal dildo can be a personal and subjective decision, but here are some factors to consider when making your selection:

1. Size and shape: Glass and metal dildos come in various sizes and shapes, so consider what you find comfortable and enjoyable. Some dildos are curved or textured for added stimulation, while others are straight and smooth. Take the time to explore different shapes and sizes to find what works for you.
2. Material: Consider what material you prefer. Glass dildos are known for their beautiful aesthetics and can be used for temperature play, while metal dildos can also be used for temperature play and have a smooth, polished surfaces. Both materials are non-porous and easy to clean.
3. Quality: Look for a high-quality glass or metal dildo made from medical-grade or body-safe materials. This will ensure that the dildo is safe to use and will last a long time with proper care.
4. Brand reputation: Research the brand before making a purchase. Look for brands with a good reputation for producing high-quality, body-safe sex toys. Read reviews from other users to get an idea of the toy's performance and quality.
5. Price: Glass and metal dildos can range in price depending on the brand, size, and material. Consider your willingness to spend and whether the toy's features and quality justify the price.

Remember to always use plenty of water-based lubricant with your glass or metal dildo and check the toy for any damage or cracks before each use. With proper care, a high-quality glass or metal dildo can provide long-lasting and enjoyable use.