I think the big difference is the Plus has the single point watering system vs the regular 105's which has the Hydrolink watering system if you want to use it. The regular 105's also has the EUT terminal option which the Plus doesn't.
If you go with Trojans though and want bolt on terminals, I would suggest you go with the EHPT (embedded high profile terminial) post. The difference is the ability to stack more than 2-4/0 or 2/0 battery cables per post. With the standard post, the ELPT (embedded low profile terminal) you are limited to ~2. If you look at the lower right terminal, I have 1-4/0 and 2-2/0 lugs on the post. I would like to have a little more post height.
Shop around for prices. This spring we replaced ten (we had the cores) for less than $100/each at a golf cart store.
Edit: When we picked up our batteries, the seller went out of his way to stress that we use the correct torque for the nuts on the posts. He showed us 2 new batteries where a buyer (s) got a little carried away over tightening the nuts. Trojan lists the torque value at 95-105 in-lb for the ELPT or EHPT posts.