Belgium citizenship

The pros are you get to live/work/study anywhere in the EU and use an ID card to travel around the EU, plus you get to vote in all elections in Belgium.

Not sure there are any "con's".

You need to go through the naturalization process. You haven't asked about this, so I'll assume you know what you need to know.

Belgium allows dual nationality, so no issues at all with 2 passports.

Pros:
- You get all the benefits of being an EU citizen and won't lose them on Brexit
- You get to vote

Cons:
- You may be eligible for jury service and election duty
- You have to vote

Requirement for jury service ceases at age 65.

The passport is much cheaper as very easy to renew at your local Commune down the road.

Once you are a citizen and have your Belgian ID card you can also travel all around the Schengen area + Ireland (and I think some other extra EU countries (Turkey? - but do check) without having to carry your passport with you.

A Belgian adult passport is actually more expensive than a British adult one issued in the UK when calculated on a yearly cost.

GBR adult passport issued in the UK = £85.50 or 96 euro or 9.60 euro for each year.

BEL adult passport issued in Belgium = 75 euro for 7 years or 10.71 euro for each year.

The cost of the passport is irrelevant.
If you have a British one you won't need a Belgian one as you can travel widely with your Belgian ID. Certainly throughout Europe, with the exception of Russia and Belarus, and a wide range of other countries so long as the visit is as a tourist. The rules do change from time to time but we've been to Turkey, Tunisia and Egypt and I think we used Belgian ID for Thailand as well.

And if you live in Belgium, as the OP obviously does, a British passport will set you back £106 or €121 (plus a four week wait if you're lucky). But the good news is they're not yet issuing the blue ones!

"And if you live in Belgium, as the OP obviously does, a British passport will set you back £106 or €121 (plus a four week wait if you're lucky)."
But first you have to find a photographer that can cope with the UK's non-standard choice of background colour(s). Doubtless that isn't a problem in Bruxelles but some of us live a long way from there.

"But first you have to find a photographer that can cope with the UK's non-standard choice of background colour(s). Doubtless that isn't a problem in Bruxelles but some of us live a long way from there." Good point. Top tip for this is the Mister Mint in the Auderghem Carrefour hypermarket. Handy if you're coming down the E411 and don't want to go into the centre of BXL.