Comparing apples-to-apples using April 1955 timetables (New Haven
NHV-SPG: 1:14 to 1:43, typical 1:30
SPG-WOR: 1:02 to 1:50, typical 1:15
Typical through schedules with a transfer at SPG were about 2:45
NHV-NLC: 0:52 to 1:20, typical 1:00
Typical through schedules with a transfer at NLC were about 2:50
Current typical times are 1:30 NHV-SPG, 1:20 SPG-WOR, and 0:50 (Amtrak) to 1:15 (SLE) NHV-NLC - comparable to the 1955 schedules.
So, it's about a wash on travel times. Going via Springfield will always have better ridership because of the larger cities, but NLC-WOR would probably be a respectable secondary route with decent connections at both ends. The similar travel times would actually be good for connections; for example:
A northbound Regional arrives at NHV at 11:50 and leaves at noon.
An Inland Route train also departs at noon, reaching Springfield at 1:30 and proceeding east.
The Regional reaches at NLC at 12:50 and continues eastward.
A shuttle train departs NLC at 1:00, reaching Worcester at 2:45.
The Inland Route train also reaches Worcester at 2:45. It takes on connecting passengers from the shuttle and continues eastward, reaching Boston before 4:00.