Junior agent v. agent

Sat Nam! (literally "Truth Name"--a Sikh greeting)

Go with the agent who seems like the best fit for you. If both seem about the same, then go with the one that asks for what lets your book shine better.

Blessings,

Siri Kirpal

The junior agent may be the one who is building their list and will take on ten clients this year. The senior agent may well have a mature list and only add a client if they come across something they really love.
How lucky are you feeling?

A senior agent will have more clout in the publishing world, but will likely have a large client list already and be less likely to take you on unless he/she absolutely loves your work (it happens), and when they do sign you up will rightly have to give established clients more of their energy and you'll need to be prepared for that. But they won't ignore you, it may just take a little more time to hear back from them if they are having a crisis with one of their established clients etc.

The junior agent could still have some clout because of their agency attachment, but may not have as good connections. With a small list and getting in early on that list they'll have more time for you, which useful if you need more editorial input, and it could be argued that there's more chance of being signed, but if they don't seem a good fit it's less likely they will connect with your work in any case so don't just go with a junior for that reason.

If you find a big agent who seems right, go for it. The connection should be the most important thing. But if you were deciding between 2 agents who seemed like they would both be as connected to your work you should weigh up how much support you are likely to need as you take your first steps in publishing (junior) versus feeling ready and looking for a big deal (senior).