I'm not sure who I know is definitely an ESI, so this answer might sound a bit speculative. In a highly general and superficial way, I do admire ESI's sense of deep trust and loyalty (especially as an Enneagram 6). However, I tend to think that the manner by which they do this would come out as being way more restrictive than I might like. I can see ESIs having a hard time having certain people enter their inner circle. I'd rather live more openly and friendly than being really restrictive over who enters this 'trustworthy' space. I abhor the idea of feeling tested at every second for acceptance into their inner circle. I'd rather have things be relaxed and kick-back than anything else.
I also, see their
value as being quite aggressive and pushy. While I admit that sometimes a modicum of
in this competitive world is a good thing, I cannot stand living my life solely on those principles. This also leads to an increased judgmental style of ESI that would not necessarily exist for the EII. It sounds as if everything has a cutthroat ('What have you done for me lately?') style that I am not a fan for. Why should I have to feel scrutinized all the time and potentially rejected in a prompt, aggressive manner in a New York minute.
So even though I do not know a confirmed ESI for sure, I would imagine that this would conflict quite easily and obviously from my personal style and preference. Ironically, I can easily see ESIs as Enneagram 6s, and I, myself am a 6. Yet, 6s are known to span the entire typological domain (especially with regards to phobic and counterphobic) and I feel like a very different style of 6 than a staunchly mistrusting (guilty until proven innocent) 6 which feels quite ESI'ish.
I think that the academic interests of the ILI feel a bit more comfy and collaborative than the ESI style. (As stated above) I do admire the trust/loyalty feel of the latter type; yet, the specific manner by which this is accomplished is probably more of a turn-off than the generally reclusive and terse academic style of the ILI. I think that at least for the ILI, common academic interests could keep the momentum going half decently. For ESIs, the relative absence of this would make things even harder.