Hi all
Actually, this question opens up a can of worms, regarding evolution. Most texts seem to repeat the assumption that short tongued bees have an advantage because they are "generalists" while long tongued bees being specialists, cannot readily adapt. There are other points of view

Specialization is due to length of life cycle and seasonal flight time:

Lovell (1914) in his studies of bees
in Maine argued that it is not an advantage to be
restricted to one kind of flower. He supposed that
specialization would be disadvantageous since the
bees would then have only a narrow food base.

Robertson (1914) stated that >40 species of halictines,
were flying throughout the season;
most of the other solitary bees had short flight times.
The latter were restricted to the flowers of specific
plants, and the former were not. 

Heinrich (1976) Resource Partitioning Among Some Eusocial Insects: Bumblebees

* * *

Long tongue bees are not disadvantaged:

In general, bees with longer tongues visit a greater number of nectar hosts than bees with shorter tongues, and flowers with longer tubes tend to have fewer visitor species than flowers with shorter tubes. This finding is significant because other recent studies have revealed spurious correlations between nectar tube length and visitor diversity when phylogenetic covariance has been taken into account.

The present results demonstrate that bee species generally forage at any flowers from which they can physically extract nectar, a finding that supports Roubik’s (1992) suggestion that euglossine bee communities are not partitioned on the basis of differences in tongue length alone.

Borrell (2005) Long Tongues and Loose Niches: Evolution of Euglossine Bees and Their Nectar Flowers

* * *

In short, the long tongued bees do not appear to have a disadvantage due to tongue length at all, while the time window in which a species is alive and foraging is an critical factor. 

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