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I don't think that there is a way to tell visually and certainly a lot of them look like GCs. I think the decision is based on assessment of star numbers and spectroscopy - using metallicity to determine the age etc. The story of GCs in the LMC seems to have changed somewhat over the last 15 years or so as it seems that the age and structure of GCs there differ quite a lot from the Milky Way with the LMC GCs being younger, bluer and with fewer stars. So at some times a lot of these seem to have been classified as "Blue Globulars" or "Young Populous Clusters".
From what I've been able to gather there are 13 official GCs in the LMC and I haven't found a definitive list of them so far. I have a way to go in reading the literature though and a fair whack of it is above my amateur head. So I've relied on the NGC/IC project for determining what classifications to use for objects on the charts.
It does seem that the issue comes down to when do you call something a globular cluster.
Any input from someone who knows what they are talking about would be much appreciated.
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