This really is the first decision to be made. The choice will come down to a variety of factors which I list below. You can then make up your own mind which is the more suitable.

In the meantime let me just dispel one myth; grass seed does not necessarily make a better quality lawn than turf. The quality can easily be the same; however, the range or choice of types of lawn is generally far greater with grass seed allowing you to have exactly the right type of grass for your needs.

Seed sheets are an alternative seeding method. They aren’t cheap and require sound installation but once achieved work very well. They are worthy of consideration for steep slopes where seed may wash away.

Advantages of Grass Seed

• At least a tenth of the price of lawn turf therefore the most cost effective
• For small areas or repairs it is the perfect hassle free solution
• More choice of lawn type from ornamental to play lawns and shady to drought tolerant lawns
• Tends to acclimatise better in difficult conditions e.g. shade or heavy soil
• Very easy to spread lawn seed by hand or with a spreader
• Can be sown in a tenth of the time compared to turf
• Easy to store and light to carry
• Will keep for several years
• Preparation is the same as for turf
• Can usually buy the same or very similar lawn seed for repairs years later

Disadvantages of Grass Seed

• Not very ‘instant’; needs a couple of months to establish
• Heavy rain will wash seed off slopes
• Can be prone to attack by birds
• Needs more aftercare for the first month than turf

Advantages of Lawn Turf

• Visually it’s an instant lawn and can be used (gently) within a month or so
• For small areas or repairs where cost is not so important it is good but time consuming
• Won’t wash off slopes during heavy rain like grass seed
• Less watering required after sowing than seed; still needs some though
• Preparation is the same as for seed
• Turf laying can be done all year round but makes for a perfect winter job!

Disadvantages of Turf

• Cost; can be expensive for large areas
• Limited choice readily available
• Doesn't aclimatise very well to shady or wet areas
• Needs to be laid as soon as possible after delivery

Summary

All things being equal I would turf slopes and modest areas that are affordable. For larger areas, areas difficult for growth such as shade or where I require a certain type of grass then I would always seed. Both take about a year to be fully mature and be tough enough for serious use.