Buying plants on line from any nursery can be a real experiment for anyone. It is important to be sure to know what size and quality of plant you are buying. There are Canadian and US standards for nurseries to use.
For example prices may be deceiving. Be sure to check that the actual size of the plant is listed. Thus you have an idea what you are buying. A perennial may be easier to buy because they are sold as divisions. But a shrub or lilac are different. I have seen plants listed for example at $12.95 and it makes the plant look inexpensive. But with further investigation on smaller lines the lilac is in a 4"pot.

Another company offering the same lilac was selling there 1 gallon 12" plant for $16.00. A larger pot means more branching and thicker stems but the size is also denoted so you know you will get a plant that is minimum 12" in height. Other companies may give you a size variance from 12" to 24" for example. Nursery standards that are commonly used are 3,6,12,18,24,36".

Both plants should do fine when planted but it is the cost versus size that gets you more for your money.