Let's see why Arista constantly outperformed its industry peers as Juniper remained a laggard and whether that trend will continue in the future.

The key differences between Arista and Juniper.
Arista sells network switches that are optimized for software defined network (SDN) solutions. This means that their switches are less powerful than traditional Cisco switches, but they are cheaper and depend on their cloud-based EOS platform to do the heavy lifting. Arista also offers an open source version of EOS for "white box" networks, which use generic hardware.
SDN solutions and white box networks are cheaper, more flexible and more scalable than the hardware and software packages of companies such as Cisco, which ensure enterprise customers all-in-one solutions. Arista also believes that it can completely replace traditional routers with its FlexRoute software.
Juniper sells mainly traditional routers and switches. But like Arista, Juniper also expanded to the cloud market with its QFX switches for data centers. He also introduced new SDN solutions and launched optimized routers for SDN.
However, Juniper's transition from more expensive hardware to cheaper cloud-based hardware accelerated the growth of its revenue and profits in recent years. Meanwhile, the increase in virtualization (which requires less network hardware on the site), the growth of SDN players like Arista and the increasing adoption of white-box hardware exacerbated the pain.
How fast are Arista and Juniper growing?
Arista's participation in the global exchange market increased from 5.5% to 6.6% between the second quarter of 2017 and 2018, according to IDC. The firm contributed that growth to Arista's growth in hyperscale markets and public cloud providers. The company does not sell traditional routers.

During the same period, Juniper's share in the switching market fell from 4.3% to 3.8%. Their participation in the market of business routers and service providers also decreased from 14.6% to 12.8%. It seems that the company is getting lost in the confusion between the hardware players of larger traditional networks like Cisco and Huawei on one end, and the disruptive SDN players like Arista on the other.
That's why Arista's revenue and earnings growth consistently outpaced Juniper's numbers over the past year.