I believe they are two similar but distinct theories of underdevelopment: one relates to the American-Marxist model, the other to the Latin American-Structuralist model. There is clearly some discussion about how these different models relate to each other and what role the Cepal had in both approaches. Your author probably has a definite idea as to how these terms should be distinguished and hence the use of both. I would follow his or her lead and use Cepalist for cepalino and dependency theorist for dependentista.

The UNAM link below looks to be a good reference for English terms in my view.

There are two dependency theory traditions, namely: the American-Marxist developed by Baran, Sweezy and Gunder Frank, with important ramifications in the works of Dos Santos, Marini, Quijano and Bambirra; and the Latin American- Structuralist that builds on the work of Prebisch, Furtado and Anibal Pinto at the Economic Commission for Latin America and the Caribbean (ECLAC),2 and also on Marxist historians such as Bagú and Caio Prado and is best represented by Cardoso and Faletto, Conceição Tavares, José Serra, Cardoso de Mello, Sunkel and Francisco Oliveira.
http://www.economia.unam.mx/cegademex/DOCS/matias_vernengo1....

1.2 Las teorías cepalina y de la dependencia.
La teoría del subdesarrollo de la CEPAL , que tiene en Raúl Prebish a su principal exponente y fundador, surge en buena medida como una crítica a los magros resultados que la aplicación de las tesis modernistas habían reportado en el desarrollo de la región. La principal crítica se orienta al mercado como mecanismo espontáneo de solución de los obstáculos que interna y externamente se oponen al desarrollo de América Latina.
...
La teoría de la dependencia surge como una respuesta al declive de la teoría del subdesarrollo en la región, de la cual retoma el esquema bimodal para explicar los problemas de atraso de la región, aunque su principal influencia proviene del neomarxismo.
http://www.eumed.net/tesis-doctorales/2011/hfl/teorias.html