Barb certainly can help you with the best options on the peninsula.
I would just put in my two cents' worth:
Robert's Grove and Turtle Inn are in a separate class from the rest of the properties on the peninsula. Both are terrific but quite different. Robert's Grove now has THREE pools and Turtle Inn has two (though one is usually reserved for guests at Coppola's cabanas -- I did swim in it once but actually prefer the main pool.)
The newly built villa units at the south end at Robert's Grove look fabulous. In fact, any of the condo units at Robert's Grove are amazing. At Turtle Inn, because there's no A/C, a seaside unit is desirable especially in hot weather. I think the two-bedroom villas are just fantastic.
I first stayed at Kitty's more than a dozen years ago and it's still a favorite. The three beach cottages are just about perfect without being over the top.
Another place that has a wonderful beach and overall feel that I'm told is starting to come back after several years of decline is Rum Point Inn. I hope the turn around continues.
As to Soulshine, I know it's pleasant enough, but if you're going to go to Placencia for the beach and the sea I don't quite get why you'd want to stay at a place on the backside that doesn't have a beach and isn't on the sea.
Zeboz I think is eventually going to become quite popular, and it's certainly going to be one of the biggest places in Belize. They have plans to eventually build something like 144 units. The pool truly is amazingly big, twice as big as any other pool in Belize.
All of the hotels in Placencia village are budget to moderate, and even spots nearby like Turtle Inn are a bit too far to walk regularly. But if you don't have a car -- a rental car is handy to have on the peninsula and for day trips -- a taxi into the village is only a few bucks unless you're way up north.
If you didn't have to have a pool there are some small places like Mariposa that are really very nice.
And while Maya Beach and north of there is way away from things in Placencia village, there is starting to be some top options up there, like the bistro at the Maya Beach Inn.
From memory, here are the resorts with pools on the peninsula. I probably have left at a couple. They are listed roughly in order from north to south.
Luba Hati (not sure what the current situation is)
Inn at Robert's Grove (3 pools)
Rum Point Inn
Turtle Inn (2 pools)
Just as a point of interest, I'd note that of these places five are on the market and have been for a long time. That's one of the differences between San Pedro and Placencia -- the level of busines year round. Only a few places on the peninsula, like Robert's Grove, Kitty's and Turtle Inn, stay busy much of the time.