An arena and enlarged convention center are not one in the same even if their was an option to do both. Leaving the enlarged convention center out of it, what specifically does a new arena do to justify it's immense cost?
With an enlarged convention center, what extra conventions is Baltimore competing for?
Well, as of 2013... Baltimore had fallen from around 35th to 75th nationally in convention space... with expectation of falling into the 100s within 5 years...
As far as what convention events... Baltimore is now missing out on numerous conventions, with similar sized markets taking more of their share... and without the ability to compete for the larger events.
And yes, Arena space is directly correlated as well.. so there is no way to leave that out of it realistically... but to play along...
1) Conference tourneys: Big Ten, ACC, A10, CAA, MEAC...
(Currently has hosted CAA, so agree not fair to list... but using myself as an example... I will never go to the existing Arena... I would consider something like the CAA tourney at a new Arena.)
2) NCAA Regional... hasn't happened since Big Country Reeves / OKST...
3) NBA / NHL exhibitions... both happen now, but might have slightly more regularity. Also might get handful of regular season games as once existed with the Bullets.
4) Something similar to the BB&T Classic... venue for Towson, UMBC, Loyola, Coppin, Morgan to bring in larger OOC opponents.
5) Obviously all current events... with a higher level of better concerts... admittedly, the existing Arena has upped their game in recent years and brought in a better caliber of acts.
6) Arena Football, WNBA, etc
None of that more important vs. the help it would give to conventions.
You would want a space that had the requisite amount of skyboxes, and total seats that it could 'play up' in time if there was eventually enough corporate dollars to go around to support a 3rd Major League team in the city... vs building something from the beginning which would never be capable.