Although more costly, IaaS offers the most control over the type of compute unit (Basic, Standard, Premium, A0-4, D0-4, etc) which determines vCPU, Memory, Network, SubNetwork, Storage options (SSD, Size, etc.) and more.
On the other hand, as Azure doesn't have know what you will get up to, standard services won't be enabled by default, and you are responsible for configuring:
| Size | CPU |
|---|---|
| A0 | 50 |
| D1 | 160 |
New-AzureRmCM -ResourceGroupName $rg -M $vm ..